I cancelled this order and want to know how to get a refund from Apple

Click ▶︎ Request a Refund.

According to Apple:

If your refund is approved, the funds are applied to the same payment method that you used to buy the item.

Here's how long it takes for a refund to appear on your account or statement:

Store credit—It might take up to 48 hours to see the refund in your Apple ID 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.

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.

Click ▶︎ Check Refund Status.

See information in Request a refund for apps or content that you bought from Apple - Apple Support