Yes you’d need to set up your products in the cart66 plugin as well. Try it out with one product. As soon as you’ve created one you can select it in the dropdown on the posts you created for the menucard. This way you can link the menucard posts to the cart66 products.
You can check the cart66 website to see if the free version would fit your business: https://cart66.com/features/
Hope this helps 🙂