Recently updated to Sonoma 14.0, now all files on my computer are gone (no files show on desktop)... how can I recover them

Go into System/Apple ID/iCloud setting pane and see if iCloud Drive is enabled. If it is click on iCloud Drive and see of Desktop and Documents is also enabled.

If they are then disable them and select the option to keep a copy on the Mac.

When upgrading to a new system often we are asked if we want to enable iCloud Drive. Many have done so automatically without considering what it means. Let's hope this is the case. 🤞

Not unless you just happen to have copies somewhere or kept your data in iCloud.

Backing up is a standard practice of making automated regular copies of all your data. The built in app for that in macOS is Time Machine. It's designed to allow for recovery after things that cause data loss, but the user has to set it up and get it running.

You don't know about backing up?

Have you searched you drive with Spotlight?

Look in you User/Home/Library/Mobile Documents folder:

If you turn off iCloud Drive you should have gotten this window:

Look for your files in the Users/Home/iCloud Drive (Archive)

Go to the finder>desktop to see if your files are there.

Otherwise, you can restore them via a Time Machine backup

You have to have made them on an external drive. They aren't built in (the app is) and it takes a human to set up backing up.

What did you find? Was iCloud Driver enabled and was Documents and Desktop enabled? Can't go further until I know what you found.