Hello @BrandyHayes thanks for your question. Check out this post about creating QR codes for checkout:
https://www.sellercommunity.com/t5/Questions-How-To/How-do-I-set-up-a-qr-code-that-customers-can-sca...
I'm not exactly sure what your looking to do with QR codes, but the above tutorial walks you through the steps to create QR codes per ITEM. Your customer would scan the QR code to pay and purchase a specific item. Are you looking for a QR code that would take them to your online store?
If you are working in-person at a craft show, it's likely that your customers will purchase (hopefully) more than just one item; QR code scan to shop only allows for a single item purchase (I think). It would be better to use your Square phone App (or ipad app) when you are doing a craft show to tally up a customers order, and then swipe or scan their payment card.
