I need my Excel to continue to work on my MacBook Pro

This is a user to user forum, nobody here is messing with your computer. If you just updated your macOS version, then your version of Microsoft Office might not be compatible with the new macOS version.

Nobody did this but you. You and you alone updated the Mac.

If you had a 32 bit 2016 Microsoft Office, it will not run on newer operating systems starting with macOS 10.15 Catalina.

You would need to purchase a new version of Office from Microsoft

Or use a free alternative to access your MS files such as LibreOffice or Apple's own free apps such as Pages, Numbers and Keynote.

click here to purchase a new version of Microsoft Office ➜ https://www.microsoft.com/en-us/microsoft-365/mac/microsoft-365-for-mac

click here to download LibreOffice ➜ https://www.libreoffice.org/

click here to download Apple's Numbers ➜ https://apps.apple.com/us/app/numbers/id409203825?mt=12

click here to download Apple's Pages ➜ https://apps.apple.com/us/app/pages/id409201541?mt=12

If you have issues with Excel, contact Microsoft.