how to get an item from a data source within a repeater

Question

i have a list of items within a repeater and im trying to get the index of each item after clicking a button and inserting the data into another table.i tried almost everything but cant find how to make it possible. the code below is the one i used to retrieve the data from the db and display it on the repeater :

 

 

protected void Page_Load(object sender, EventArgs e)

     {   

        con.Open();  

        SqlCommand cmd = con.CreateCommand();

        cmd.CommandType = CommandType.Text;

        cmd.CommandText = "select caract, image_Ter, taille, info from Terrain";

        cmd.ExecuteNonQuery();

        DataTable dt = new DataTable();

        SqlDataAdapter da = new SqlDataAdapter(cmd);

        da.Fill(dt);

        temp.DataSource = dt;

        temp.DataBind();

        con.Close();

      }

and heres the button that i want it to get the index and insert the data into another table :

<asp:Button class="btn btn-secondary btn-xl" data-dismiss="modal"      runat="server" ID="choice" Text="Add" />