MarketPress item item display order

I am working with the MarketPress plugin, and I have created a page that displays all my products. I have told it to order them by “ID” however; there is no “ID” field when creating new products inside of MarketPress. I assume that it means “SKU” and I have created SKU numbers; however, when I have told it to order them by “ID” and I have told it “ascending”, it is not displaying the items in the proper order. How can I get them to display by SKU? Or how can I set the “ID” if ordering by SKU isn’t possible. Here is the page in question: http://www.mcgolf.com/pro-shop-products/

Thanks,

Sean McLellan