iCloud backup has disappeared on my Mac

Macs don't back-up to iCloud. Word and excel files would only be in iCloud if you manually put them there through Finder or have the Desktop & Documents option turned on in System Preferences->Apple ID / iCloud ->iCloud Drive->[Options].

Otherwise if using Microsoft's Office 365, they may store the files on Microsoft's own cloud storage called One Drive.

Can you tell us what steps you normally followed to find your documents and excel spread sheets?

Did something happen recently that may have led to your files no longer being accessible?

What macOS version are you running on your Mac? Check the Apple Menu->About this Mac.

There seems to be a an issue with terms and context.

Please explain exactly how you were saving your files to iCloud. What exactly were you doing to save them there?

Paying .99c for iCloud does not mean everything it just automatically saved to iCloud.

Where exactly do you normally find your files? do you just open your Word and Excel Apps and they appear there? Or are you opening them form the Finder application? If so where in Finder exactly?

Again, please answer the questions:

Can you tell us what steps you normally followed to find your documents and excel spread sheets?

Did something happen recently that may have led to your files no longer being accessible?

What macOS version are you running on your Mac? Check the Apple Menu->About this Mac.

Your serial number is not helpful for this matter. Please do not post it in a public forum.