Where your receipt comes from depends on where you subscribed.
App Store purchase. Apple issues the receipt. Check the email tied to your Apple Account, your App Store purchase history, or reportaproblem.apple.com. Aura cannot create or edit Apple's receipt because we never process that transaction.
Website purchase. Start with the receipt sent to the email you used at checkout. If it is missing or does not include what you need, email help@downloadaura.app with the purchase email and the details you need shown.