Where did my iCloud files go?

Manually moved all the content from my iMac into iCloud b/c I didn't see a way to simply back up my machine to iCloud. Some large files were stuck in an uploading status for a few days and I'm not sure if the upload was completed, but they weren't important files. The important files were already uploaded to iCloud. Reinstalled OS. ALL the files that were previously in iCloud uploaded from this machine are gone.

A) Where did my files go?
B) Is there a way to just select "backup to iCloud" or something? I'm paying for 2TB, I should be able to back up my machines, right?
Where did my iCloud files go?
 
 
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