During the install process you are asked if you want to use iCloud Drive. If you miss the opportunity or say "no", then all the iCloud files are dumped in an "iCloud Archive" folder in Finder. So much depends on your previous use of iCloud for files, or not.
Another repercussion is that the option to use iCloud for "Documents and Desktop" is unchecked. I got both iCloud and local folders appearing in Finder, which is very confusing.
If you go to Settings>AppleID and check to use iCloud, also check the above option to use Documents and Desktop from there too. Your iCloud files will take some time to download again onto your computer, but there is a "download now" option on the folder.
I keep all my files in the iCloud Documents folder and moved them out of the individual iWork app folders, which I find irrelevant to a project based filing system. I then slide the Documents folder into the Finder sidebar for easy access.
If you really want fun you can view the hidden files from both systems, to see if your missing ones just got hidden, but I would not recommend it for the faint hearted.
https://www.howtogeek.com/211496/how-to-hide-files-and-view-hidden-files-on-mac-os-x/
