After you buy something on the Google Store, you get a confirmation email that you can use as a receipt. You can find your order number on this receipt.

If you can't find your confirmation email, you can get a receipt online:Google:
- Visit
- Sign in with your Google account.
- On the left, click Activity.
- To get your receipt, select an order.
-Login to your Apple Store and tap on the icon in the upper right of your screen.
-Tap your Apple account and choose the purchasing record.
-Choose the purchase receipt you want to get.