When a transaction/payment has been refunded, the money will be credited back to the same funding source that was used to pay originally.
If you paid with a debit card/bank account, the refund should appear between 5-7 working days on your card/bank statement.
If you paid using a credit card, this refund can take anything up to 30 days to appear on your statement.
If your PayPal balance was used to fund this transaction, you should see the refund credited to your PayPal balance immediately. You can check what funding source was used by finding the original payment on the Activity section of your PayPal account.