Your Trek bike has standard road wheels. They come in various widths but they have a 700 designation with a second number like 25, 28, etc that's the width. You probably should get the same size as you have now and the size is on the sidewall. For example it might say 700x28

The two largest sellers are Michelin and Continental. Each has several models. But if you like the Trek (Bontrager), stick with them