cleaning up c# code which connects to sql database using windows form

Question

All I would like is for help with putting this code into separate classes as I cant seem to figure it out. I would just like to understand how this would be possible with this set of code.

using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace FinalDatabaseConnection {
    public partial class Form1 : Form {

        public Form1() {
            InitializeComponent();

        }

        //if statment dealing with sql queries once button hit
        private void button1_Click(object sender, EventArgs e) {
            lblCompleteItemInfo.Text = ("");
            String source = @"Data Source=WIN10-LAP->HJP\MSSQLSERVER1;Initial Catalog=VisualStudioConnect;Integrated Security=True";
            SqlConnection con = new SqlConnection(source);
            con.Open();

            if ((string) cbfunctionSelection.SelectedItem == "Find" && checkBoxPCSearch.Checked) {

                String sqlSelectQuery = "SELECT * FROM Items Where PartCode = @SelectedPartCode";

                var cmd = new SqlCommand(sqlSelectQuery, con);

                SetInsertParameters(cmd);
                SqlDataReader dr = cmd.ExecuteReader();
                SetResponse(dr);
                AllVisible();

            }
            else if  ((string)cbfunctionSelection.SelectedItem == "Find" && checkBoxNameSearch.Checked) {
                 checkBoxPCSearch.Checked = false;
                String sqlSelectQuery = "SELECT * FROM Items Where Name = @SelectedName";

                var cmd = new SqlCommand(sqlSelectQuery, con);

                SetInsertParameters(cmd);
                SqlDataReader dr = cmd.ExecuteReader();
                SetResponse(dr);
                AllVisible();
            }

            if ((String) cbfunctionSelection.SelectedItem == "Add") {
                 checkBoxNameSearch.Checked = false;
                var cmd = new SqlCommand(
                    "INSERT INTO items(Description,Colour,Manufacturer,StockLevel,Name) " +
                    "VALUES ( @Description, @Colour, @Manufacturer, @StockLevel,@Name)", con);
                SetInsertParameters(cmd);
                cmd.ExecuteReader();


            }

            if ((string) cbfunctionSelection.SelectedItem == "Delete") {

                var sqlDeleteQuery = "Delete from items where PartCode =  @SelectedPartCode" ;
                SqlCommand cmd = new SqlCommand(sqlDeleteQuery, con);
                SetInsertParameters(cmd);
                SqlDataReader myreader;
                myreader = cmd.ExecuteReader();
                myreader.Read();
            }

             if ((string) cbfunctionSelection.SelectedItem == "Edit") {

                var cmd = new SqlCommand("update items SET Description = @Description ,Colour =@Colour ,Manufacturer = @Manufacturer,StockLevel = @StockLevel , Name = @Name where partcode = @SelectedPartCode", con);
                SetInsertParameters(cmd);
                cmd.ExecuteReader();
            }

             else {
                 MessageBox.Show("PLease refrence the helper text box for help i");
             }

            con.Close();
        }
        //setting the response for the find function


        private void SetResponse(SqlDataReader dr) {

            if (dr.Read()) {

                string itemDescription = (dr["Description"].ToString());
                txtColour.Text = itemDescription;

                string itemColour = (dr["Colour"].ToString());
                txtColour.Text = itemColour;

                string itemManufacturer = (dr["Manufacturer"].ToString());
                txtColour.Text = itemManufacturer;

                string itemStockLevel = (dr["StockLevel"].ToString());
                txtColour.Text = itemStockLevel;

                string itemName = (dr["Name"].ToString());
                txtColour.Text = itemName;


                string itemPartCode = (dr["PartCode"].ToString());
                txtColour.Text = itemPartCode;

                lblCompleteItemInfo.Text = ($"The items description is: {itemDescription} " +
                                            $"The items colour is: {itemColour} " +
                                            $"The items Manufacturer is: {itemManufacturer} " +
                                            $"The Items Stock Level is :{itemStockLevel} " +
                                            $"The Items Name is: {itemName} " +
                                            $"The items PartCode is: {itemPartCode} ");    

            }

            else {
                MessageBox.Show("error");

            }
        }
        //applying the values for sql queries through the input in tbox
        private void SetInsertParameters(SqlCommand cmd) {

            cmd.Parameters.AddWithValue("@Description", txtDescription.Text);
            cmd.Parameters.AddWithValue("@Colour", txtColour.Text);
            cmd.Parameters.AddWithValue("@Manufacturer", txtManufacturer.Text);
            cmd.Parameters.AddWithValue("@StockLevel", txtStockLevel.Text);
            cmd.Parameters.AddWithValue("@Name", txtName.Text);
            cmd.Parameters.AddWithValue("@PartCode", txtPartCode.Text);

            cmd.Parameters.AddWithValue("@SelectedPartCode", txtPartCodeEnter.Text);
            cmd.Parameters.AddWithValue("@SelectedName", txtNameEnter.Text);
        }


        private void AllVisible() {
           //txtboxes
            txtDescription.Visible = true;
            txtColour.Visible = true;
            txtManufacturer.Visible = true;
            txtStockLevel.Visible = true;
            txtName.Visible = true;
            txtPartCode.Visible = true;
            txtPartCodeEnter.Visible = true;
            txtNameEnter.Visible = true;
             //lbls  
            lblDescription.Visible = true;
            lblColour.Visible = true;
            lblManufacturer.Visible = true;
            lblStockLevel.Visible = true;
            lblName.Visible = true;
            lblPartCode.Visible = true;
            lblNameEnter.Visible = true;
            lblPartCode.Visible = true;
            checkBoxNameSearch.Visible = true;
            checkBoxPCSearch.Visible = true;
        }

        private void cbfunctionSelection_SelectedIndexChanged(object sender, EventArgs e) {
            if ((String) cbfunctionSelection.SelectedItem == "Add" ) {
                AllVisible();

                checkBoxNameSearch.Visible = false;
                checkBoxPCSearch.Visible = false;

                txtPartCodeEnter.Visible = false;
                txtNameEnter.Visible = false;
                txtPartCode.Visible = false;

                lblPartCode.Visible = false;
                lblNameEnter.Visible = false;
                lblPartCode.Visible = false;

                HelpLabel.Text = ("input the details for the item to be added.");
            }
            else if ((String) cbfunctionSelection.SelectedItem == "Find" ) {
                AllVisible();
                txtDescription.Visible = false;
                txtColour.Visible = false;
                txtManufacturer.Visible = false;
                txtStockLevel.Visible = false;
                txtName.Visible = false;
                txtPartCode.Visible = false;

                lblDescription.Visible = false;
                lblColour.Visible = false;
                lblManufacturer.Visible = false;
                lblStockLevel.Visible = false;
                lblName.Visible = false;
                lblPartCode.Visible = false;

                HelpLabel.Text = ("input the Partcode of the item and the information will be displayed.");

            }
            else if ((String) cbfunctionSelection.SelectedItem == "Edit") {
                AllVisible();
                lblPartCode.Visible = false;
                txtPartCode.Visible = false;
                txtNameEnter.Visible = false;
                lblNameEnter.Visible = false;
                checkBoxNameSearch.Visible = false;
                checkBoxPCSearch.Visible = false;
                HelpLabel.Text = ("Input the partcode of the item you would like to edit. Then the Information.");
            }
            else if ((String) cbfunctionSelection.SelectedItem == "Delete") {
                AllVisible();
                txtDescription.Visible = false;
                txtColour.Visible = false;
                txtManufacturer.Visible = false;
                txtStockLevel.Visible = false;
                txtName.Visible = false;
                txtPartCode.Visible = false;
                txtNameEnter.Visible = false;
                checkBoxNameSearch.Visible = false;
                checkBoxPCSearch.Visible = false;

                lblDescription.Visible = false;
                lblColour.Visible = false;
                lblManufacturer.Visible = false;
                lblStockLevel.Visible = false;
                lblName.Visible = false;
                lblPartCode.Visible = false;
                lblNameEnter.Visible = false;
                HelpLabel.Text = ("Input the partcode of the item you would like to delete.");
            }
        }

        private void button1_Click_1(object sender, EventArgs e) {
            btnDisplayItemTable.Text = ("Refresh items table");
            //This is database connection string
            String source = @"Data Source=WIN10-LAP->HJP\MSSQLSERVER1;Initial Catalog=VisualStudioConnect;Integrated Security=True";

            //this is defining source as variable "con" to be used for SQL connection
            SqlConnection con = new SqlConnection(source);

            //opens connection
            con.Open();
            // just message box
            MessageBox.Show("connected");

            SqlDataAdapter sqlDa = new SqlDataAdapter("Select * From Items",source);
            DataTable dtb1 = new DataTable();
            sqlDa.Fill(dtb1);

            dgv1.DataSource = dtb1;

        }

        private void button1_Click_2(object sender, EventArgs e)
        {
            new Form3().Show();
        }
    }
}