What kind of barcode does my product need, and where do I get it?

I own a business and want to start selling one of my cosmetics I use everyday on my new amazon seller account, through FBM. I’m only starting with one product. I researched a bit and tried purchasing a single UPC code on gs1us.org but kept getting error codes when trying to check out. Can anyone tell me If I’m correct in the bar code I’m trying to get, and where I can actually purchase one? I’m waiting to make a bulk order of packaging until I can provide them with the barcode to print on the box.