You’ve just upgraded to macOS Catalina, and that cannot and does not run 32-bit apps.
You’re running Office 2011 or earlier here, and that and all other 32-bit apps are incompatible with Catalina and later.
High Sierra and Mojave warn about the deprecation of 32-bit apps (with Catalina and later), so that users might acquire replacements or alternatives.
Your documents are present and accessible.
For this case, you will need to purchase and use Office 2019, the Office 365 subscription, or the upcoming Office 2021. Office 2016 is also 64-bot also also works, but that’s no longer available for purchase.
Or acquire an alternative, such as the free LibreOffice package.
The Apple iWork apps can also read and write many Office documents.