How do I transfer my Apple Store Gift Card balance to the Apple Store App?

Gift cards are non-refundable and non-transferable. You may use it in Apple Retail Stores and online at apple.com/store.

>>Apple Store Gift Cards are a solid color (gray, white, silver, or gold) on the front. On the back of these cards, you can find:

• A link to a website where you can check your gift card's balance.
• Text that says that the card can only be used in the Apple Online Store or Retail Store, or that you can't redeem the card in the iTunes Store.
• A phone number that you can call if you need help.

In most countries and regions, you can use an Apple Store Gift Card in an Apple Store or at apple.com.<<

What type of gift card do I have? - Apple Support