Amazon “credit” with “gift cards” (the ones you can buy in-store)?

Hey, I'm currently building a little "business" on Discord and have a question. I'd like to add Amazon cards (the ones you can buy at Rewe and the like) to my payment options. Is there any way I can "upload"/redeem them as credit? I hope you understand what I mean. If not, just ask, and I'll try to respond as quickly as possible (I'll send you the link; it's still under construction). Please explain it for browsers or the iPad app.

Edit: I mean if I don't want to buy anything at the moment, it will be redeemed like this and the next time I buy it, it will be deducted directly