I have apple store itune gift card how to add to my apple wallet

to add to my apple wallet?

It is not possible,

Apple Pay is the way to pay. It replaces your physical cards and cash with a method of payment that is private, easier and safer. Whether you pay in a store, on a website or in an app. This is the new payment.

it is actually the same as paying contactless with your bank card, only via the iPhone.

You can add a credit, debit, or prepaid card to the Wallet app on your iPhone, Apple Watch, or other compatible device.

See -> Use Apple Pay for contactless payments on iPhone

Use Apple Pay for contactless payments on iPhone – Apple Support (UK)

I have apple store itune gift card

You can add the Apple Gift card to your Apple ID balance and use as a payment method: Add money to your Apple ID balance

Add money to your Apple ID balance – Apple Support (UK)

How to redeem your Apple Gift Card or App Store & iTunes gift card

How to redeem your Apple Gift Card or App Store & iTunes Gift Card – Apple Support (UK)

  ⤵️

Redeem a gift card with your iPhone, iPad or iPod touch

1. Find the 16-digit code on the back of the card. For some gift cards, you might need to peel or gently scratch off the label to see the code.
2. On your iPhone, iPad or iPod touch, open the App Store app.
3. At the top of the screen, tap the sign-in button  or your photo.
4. Tap Redeem Gift Card or Code. If you can’t see Redeem Gift Card or Code, sign in with your Apple ID.
5. Tap Use Camera and follow the instructions on the screen. If you have trouble redeeming the card, tap Enter Code Manually, then follow the instructions on the screen.
6. Tap Done.

See also this Apple article:  If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card

If you can't redeem your Apple Gift Card or App Store & iTunes Gift Card - Apple Support

-> You can't redeem Apple Gift Cards or App Store & iTunes Gift Cards outside the country or region of purchase. For example, if you bought an App Store & iTunes Gift Card in France, you can't redeem it in the App Store in the United States.