Printing labels from Numbers

If you aren't sure you want to upload your data to a third-party site then keep in mind there are options to stay relatively safe and secure within the Apple ecosystem.

One way is to export csv from Numbers and import your labels information into a list in the Contacts app:

Import contacts into Contacts on Mac - Apple Support

Then print your labels from the Contacts app:

Print mailing labels, envelopes, and contact lists in Contacts on Mac - Apple Support

Also keep in mind that mail merge has been reintroduced into Pages (after an absence of many years) so you can now print your Numbers data to labels and letters via Pages.

Add, change, or delete a merge field in Pages on Mac - Apple Support

SG

The easiest and most flexible method I have found it to use Avery Design & Print online. It is free and easy to use with a very small learning curve. Use Numbers File menu Export to export your Numbers spreadsheet to Excel format and then go to https://www.avery.com/software/design-and-print/