Insert multiple Rows from DataGridView to database in Windows Forms (WinForms) Application

i want to save multiple datagridview row in database 

  private void cmdSave_Click(object sender, EventArgs e)
        {
            con.Open ();
            
SqlCommand comm = new SqlCommand();
comm.Connection = con;


           string col1 = dgvChallan[0, dgvChallan.CurrentCell.RowIndex].Value.ToString();
           string col2 = dgvChallan[1, dgvChallan.CurrentCell.RowIndex].Value.ToString();
           string col3 = dgvChallan[2, dgvChallan.CurrentCell.RowIndex].Value.ToString();
         
string  sqlQury = "INSERT INTO purchaseform(ItemName,Quantity,Unit)VALUES('"+ col1 +"','"+ col2 +"','"+ col3 +"')";
        comm.CommandText = sqlQury;
        comm.ExecuteNonQuery();
          
            con.Close();
        }
}

this code is saving only one row which is last in datagrid view.how we can save multiple rows