Hey @Rcfrieworka!
Yes, you can definitely use the current/existing barcodes and do not have to generate them with Square if you don't want to.
If you scan an item (with an existing barcode) while using the Square app, the item will pop up, with the barcode, and ask you if you'd like to enter the item name and details. From then onward, the system will always recognize the item when that barcode is scanned.
If you don't want to scan in your inventory, you'll want to enter the UPC number on the product and enter that full number into the SKU field of your item. You can also do this in a spreadsheet and upload it to Square.
Here's an article on how to set up your barcode scanner initially with the app. Feel free to reply back in this thread with any questions.
