When you make a purchase on the Apple Store, a confirmation email with your order information is sent to the email address that you use to log into your Apple Account.

You can also find your order information in your Apple account by following these steps: http://support.apple.com/kb/HT2727

If you need to contact us for a purchase issue, please attach a screenshot of your receipt and make sure that the time and date of purchase is visible.

If you experience issues with this, or if you need to contact Support for a purchase issue, please submit a support ticket, by tapping the "gear" icon on the map screen, and then "support," or you can open an online support ticket here.

You can find instructions on how to take a screenshot here: https://support.apple.com/en-us/HT200289