Help with shopping cart options

You have a couple of options for your shopping cart. What I suggest is that you read this guide:

How to Integrate Form with Paypal

It shows you how to setup a basic payment integration where you specify your products. This is the easiest approach. 

This guide offers some guidance on an advanced configuration:

Mastering Payment Form Integrations with JotForm

Those two guides tell you everything you need to create a shopping cart. Should you have any further questions please get back to us and will we will be happy to help you.