It’s the cards, or rather the value of them, that are redeemed, not the Play Store.
Open the Play Store app, tap the menu bars top left, then tap Payment Method.
Welcome to Android Central! Where was the gift card purchased, and what country are you in? If the gift card was purchased in a country different from the one you're in, you won't be able to use it. See here for more details: https://support.google.com/googleplay/answer/3422659?hl=en