I has a tattoo stencil printer, and cannot find what app it belongs to

If you downloaded the app before, it will be on your purchase history. Here's how to check the purchase history in the App Store:

Find and download apps purchased by you or family members

1. Head to the App Store
2. Tap  or your picture at the top right, then tap Purchased.
3. If you set up Family Sharing, tap My Purchases or choose a family member to view their purchases.
4. Note: You can see purchases made by family members only if they choose to share their purchases. Purchases made with Family Sharing may not be accessible after the family member leaves the family group.
5. Find the app you want to download (if it’s still available in the App Store), then tap .

See Manage App Store purchases, subscriptions, settings, and restrictions on iPhone - Apple Support. Hope you get this resolved soon!