View this Support Article to see how long it may take depending on your Payment Method.
Check the status of a refund for apps or content that you bought from Apple - Apple Support
Store credit—It might take up to 48 hours to see the refund in your Apple Account balance.
Mobile phone billing—It might take up to 60 days for the statement to show the refund. Processing time might be affected by your carrier. You can contact your carrier for an update.
Credit and debit cards, Apple Pay, Apple Cash, and all other payment methods—It might take up to 30 days for the statement to show the refund. If you don't see the refund after 30 days, contact your financial institution.