See
Merge Labels Using a Down-Then-Across Output in the
Mailmerge Tips & Tricks thread:
https://www.msofficeforums.com/mail-...ps-tricks.html.
The numbering automation can be done via either a SEQ field or applying automatic paragraph numbering.
If you're not using mailmerge, simply add however many rows you need by pressing the TAB key repeatedly within the table you've created.