I need to change my credit card number

There are several ways to change you payment method, including on your computer, or iOS device, or also through the web browser. Attached here is a linked support article: https://support.apple.com/en-us/HT201266

If you want to change your payment type on an iMac, you still need to go in through the App Store app, as outlined in the support article instructions.

Set up your Apple ID payment method and shipping address on Mac https://support.apple.com/guide/mac-help/set-apple-payment-method-shipping-address-mac-mchl29cac995/mac

On iPhone: Settings > Name > Payment & Shipping