Gift card code.

So I received a gift card for the Meta and finally decided  I wanted to redeem it. When I went to scratch off the code some of it came off and it is unreadable. I tried a few different times to redeem it since I could see a very small amount of some of the taken off code. I was able to get the receipt from the store it was bought, but it doesnt have a backup code. What should I do to redeem my gift card?