how to store multiple rows in a table from gridview

protected void butapp_Click(object sender, EventArgs e)
    {
        try
        {
            foreach (GridViewRow row in GridView3.Rows)
            {
                //get checkBox from gridview
                CheckBox chk = (CheckBox)row.FindControl("checkBoxName");
                if (chk.Checked) //checking checkboxes
                {
                    //your logic goes here
                    SqlConnection con=new SqlConnection("yourConnString"); 
                    con.Open();
                    SqlCommand cmd=new SqlCommand("Insert into tableName values ('"+row.Cells[].ToString()+"','"+row.Cells[1].ToString()+"','"+row.Cells[2].ToString()+"','"+row.Cells[3].ToString()+"')", con);
                    cmd.ExecuteNonQuery();
                    con.Close();

                }
            }
        }
        catch (Exception ex)
        {
            Response.Write(ex.Message);
        }
    }