how do i find a purchase

You can view your recent purchases as explained in the support document you posted from:

You can view your entire purchase history by following the steps here: link-> See your purchase history for the App Store, iTunes Store, and more - Apple Support

See if this helps, you can -

• View your purchase history

• Cancel a subscription

• Request a refund

• Verify unfamiliar charges

• Add or remove a payment method

Subscriptions and Billing - Official Apple Support