Hello Michael_iPad,
Welcome to the Apple Support Communities!
I understand that you would like to purchase more iCloud storage but would like to know what forms of payment are accepted. Please review the attached article for this information.
iCloud storage pricing - Apple Support
Accepted payment methods for iCloud storage upgrades include credit cards, debit cards, and iTunes Store credit. If you don't have enough iTunes store credit to complete your upgrade, you'll be charged the remaining amount. Apple Store gift cards aren't accepted as payment for upgrading iCloud storage. Learn how to manage the amount of storage you're using.
Have a great day,
Joe