Hi galo911,
If your Apple Gift Card were in the Wallet app on your iPhone, you've probably already redeemed them to your Apple account. If this is the case, your Apple balance will stay in tact. If you have another device like an iPad, Mac, or computer with iTunes, you can check your balance with the instructions outlined for each on this Apple Support article: Check your Apple Account balance - Apple Support
Check your balance on your Mac
1. Open the App Store. If you see the sign-in button at the bottom of the sidebar, click it and sign in with your Apple ID.
2. If you have a balance, the amount appears below your name. If you don't see an amount, you don't have a balance.

Check your balance on your Windows PC
1. Open iTunes for Windows. If you're not signed in, sign in with your Apple ID.
2. At the top of the iTunes window, click Store.
3. If you have a balance, the amount appears below your name. If you don't see an amount, you don't have a balance.
You can also reach out to Apple Support to inquire about your Apple balance and gift cards.
Contact - Official Apple Support
Kindest Regards.