How to Add VISA gift cards

If you want to add them to your Apple account balance you will need to use them to buy Apple gift cards in a store and then redeem those.

The article "What type of gift card do I have?" explains the different kinds of gift cards Apple uses, has links on how to redeem them, and what can be purchased with each kind. Click on the link --> What type of gift card do I have? - Apple Support

How to Add VISA gift cards

You cannot add / use Visa Gift card as a payment method for the App Store, see -> Payment methods you can use with your Apple ID -> Payment methods you can use with your Apple ID – Apple Support (UK)

See here how to . . . . your Visa Gift card.