If the folder was on a separate physical or virtual (partition) drive, the upgrade may have lost that "link". Try using fdisk and other disk management utilities to search for alternate storage devices to see if it's there. If it is, you need to make sure it's mounted/remounted to be found.

Another possibility would be if your folder is part of a cloud drive (DropBox, OneDrive, iCloud, etc). You'll need to reinstall the app that controls that remote storage so files and folders appear.

You can also try the following:
Open a command prompt (Win-R or click Start and type "cmd")
In the black window, type "cd \" (that's a backslash)
Type: "dir /s *filename*" where filename is a partial string of a file you're looking for. So, for example, if you're looking for NevadaWantList.xlsx, you could type "dir /s *want*". You'll get lots of other entries if your search is too "wide", but that's ok. If it finds a file you're looking for, it will display the directory/folder just above the search results.

Not sure if any of the above applies to your situation. I hope you get it figured out.

And not that you have any reason to trust me to get on your computer, but I can do remote support where you install a small app called splashtop (http://sos.splashtop.com) and give me the 9-digit one-time access code and I can help you poke around to see what's going on (don't post it here - pm or email/call me with it - we can swap contact info via email). You can see everything I'm doing and can disconnect me any time you like. Once I log off, I would need you to give me the next unique code to get in, so it's not like I have full time access to your system. You can also uninstall the program once we're done. Anyway, throwing that out there in case you want some free tech time.