Microsoft Office 2016, Office 2019, and Office 365, are all 64-bit, and all work on macOS Catalina.
The latter two would be typical choices for new purchsses.
If you have issues, check with Microsoft Support.
If you’d like to discuss the Office issues here, we’ll need to know which Office, which version of iOS or iPadOS or macOS, what you tried, what happened, what error messages, and related details.
Alternatively, return this purchase for refund, and use LibreOffice, OpenOffice, or Apple iWork Pages, Numbers, and Keynote, and all which can read and write many Office documents.
iOS is used on iPhone and older versions on iPad, iPadOS is now used on iPad, and macOS is used on Mac. Current versions of all of these operating systems are 64-bit.