Routing and account number on Apple Cash app

Pretty straight forward. Open the Wallet app. Select the Apple Cash card, tap the action icon at the top right of the screen (three dots), tap Bank Account and enter your routing code and account number. Follow the instructions in the link below.

https://support.apple.com/en-us/HT207882

If you are asking so you can use Apple Cash for online stuff, that is not possible. There are no numbers you can attain for that card.