Office Gone

Older versions of Microsoft Office aren't compatible with Catalina.

If you have an early version of Office for Mac 2016, you can update it at no charge. See: https://docs.microsoft.com/en-us/office365/troubleshoot/administration/office-2016-for-mac-64-bit-upgrade

If you have Office for Mac 2011 or earlier, you can either subscribe to Office 365 or you can make a one-time purchase. See: https://products.office.com/en-us/buy/compare-microsoft-office-products-for-mac?ms.officeurl=mac-compare-redir

Or the free Microsoft Office on the web: https://products.office.com/en-us/free-office-online-for-the-web

Or Google Docs: https://www.google.com/docs/about/

Other options include using the free and very good Libre Office https://www.libreoffice.org/

or Apple's Pages and Numbers

No, they’re not. Your document files are still around. Your Office version is very old—2011 or earlier—and 32-bit, and incompatible with Catalina, and you’ll want to upgrade to Office 2016, Office 2019, or to the Office 365 subscription, or you can potentially use LibreOffice, or maybe the Apple iWork apps.

An issue asked and answered almost everyday.