Do you store my customers' personal data?

No. There is no column in the database for a customer name, address, phone number or email address; the schema simply has nowhere to put them, which is a stronger promise than a policy.

To tell a repeat order from a first order, nouz stores Shopify's internal customer identifier and nothing else. That is also why a data-subject request about one of your customers finds almost nothing here: your shop stays the system of record for people, and nouz is the system of record for money.