You would use our "Variants having individual price/weight/stock/SKU" and configure a line defining every possible combination, following the format indicated on the Variants screen:
For instance (and here I will change your Styles to A, B, and C for clarity) your first few Variants lines might look like this:
Itemname1-A,18.00,,,Size 1,Style A,
Itemname1-B,19.00,,,Size 1,Style B,
Itemname1-C,20.00,,,Size 1,Style C,
Itemname2-A,19.00,,,Size 2,Style A,
Itemname2-B,20.00,,,Size 2,Style B,
Here I have also presumed you are not specifying a shipping weight nor inventory stock, so I left those positions empty. The first part of each line, up to the first comma, can be anything you wish but must be unique to each line; this is a "stock keeping unit" (SKU) that you can use to identify at a glance exactly which Variant combination the buyer ordered, and if you already have your own stock numbering system, you can just use those as your SKUs here if you wish.
This will automatically add the proper dropdown menus to your Add to Cart button code we provide for the product. The first menu will show each of the different values you specified in the Option1Value position, the second menu will show those from the Option2Value position.