sinc to async

Hi all,

I have this code

	private void btnLoad_Click(object sender, EventArgs e)
        {
            FillProd();
        }

        private void FillProd()
        {
            try
            {
                dgvProd.Rows.Clear();
                var det = new Product().LoadProducts();  // 15000 ROWS
                foreach (var d in det)
                {
                    var row = new DataGridViewRow();
                    var i = dgvProd.Rows.Add(row);
                    dgvProd.Rows[i].Cells["Cod"].Value = d.Cod;
                }
            }
            catch (Exception h)
            {
            }
        }

how can I make it asynchronous?
I tried with async await, but I get cross thread error!

Thanks

d.