LOST MS OFFICE WITH LATEST OS "UPGRADE"

If it was the old 32-bit (and retired) Office 2008/2011 suites, then these are not supported on Catalina which requires 64-bit products. Thus, current Office 365 subscriptions, or the single-purchase Office 2019 for Mac are supported on Catalina.

You need to upgrade Office to 2016, 365 or higher, or downgrade to your previous version of macOS.

https://www.macworld.co.uk/how-to/mac-software/downgrade-macos-3581872/

Look into the Free LibreOffice, it handles MS Office files…

https://www.libreoffice.org/