iCloud storage full from Documents (500GB+)

I can't backup to my iCloud (without upgrading to a higher tier) because it's trying to save over 500 GB of docs. However, I'm not really sure what's taking up so much space because my apps are using only about 30 GB of space. I suspect it's got something to do with adding Dropbox and Google Drive to my Files app, but even they are only 200 GB combined. My MacBook doesn't even have 500 GB of space so it's definitely not from backing up files on my Mac.

I tried "unlinking" Dropbox and Drives by removing them from Locations in the Files app, but nothing has changed. Is there a way to free up space on my iCloud? Can I check what's actually in the 500 GB of files labeled docs in iCloud?

Thanks in advance.