how to buy icloud storage using apple gift card

See this Apple article: What type of gift card do I have?

What type of gift card do I have? – Apple Support (UK)

👉 Use your Apple Gift Card at an Apple Store to buy products and accessories. Or redeem it in the App Store and use it for apps, subscriptions such as Apple Music or iCloud+, purchases from apple.com and more. 

See the following Apple articles:

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)

Add money to your Apple ID balance

Add money to your Apple ID balance - Apple Support (IN)

Put in a different payment method. While the card's balance can be spent on subscriptions, they require having another one on file.

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