What card did I use to get my refund?

The refund can take a while to process by your bank / card issuer once Apple approves it. Up to 30 days on many cases as explained in the support document you posted from.

What I meant was, you should look for the charge you requested a refund for on your card statements to identify the card that was charged, and that will be getting the refund. The refund is always issued to the same payment method that was charged for it.

You can also verify the status of your refund by following the steps in the support document you posted from.

Only you can know what card was used. Nobody here can possibly know that.

Check the payment methods added to your account, and check your cards' statements for charges from "apple.com/bill" with the value you asked a refund for to see which one was charged.

click here ➜ If you need to change or update your Apple ID payment method - Apple Support