How to allow multithreading to generate 100000 datamatrix 2d

Question

I generating 2d matrix barcode using c# then create image file 

but when i make generating to 100000  files it make very slow and take too much time

so that i need to make multithreading but i dont know how

my code as following

string root = @"D:\" +textBox4.Text;


                if (!Directory.Exists(root))
                {

                    Directory.CreateDirectory(root);

                }
                matrixClass CLS = new matrixClass();
                DataTable dt = CLS.ShowalldataSerial(textBox4.Text);

                for (int i = 0; i <= Convert.ToInt32(textBox1.Text); i++)
                {
                    Serial = SRL.Rnd().ToString();
                    txt = "UserID" + dt.Rows[0][0] + "FirmName" + dt.Rows[0][1] + "OrderNo" + dt.Rows[0][2] + "BtachNo" + dt.Rows[0][3] + "Quantity" + dt.Rows[0][4] + "ProductName" + dt.Rows[0][5] + "SerialNo" + Serial;

                    dm.DM(txt, Color.FromName(comboBox1.SelectedItem.ToString()), Color.White).Save(root + "\\" + Serial + ".emf", System.Drawing.Imaging.ImageFormat.Emf);

                }
                MessageBox.Show("Records generated success");