Look on your desktop. Do you see a folder called; Old Firefox? Look inside. Look for the folder with the latest creation date.

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

That looks hopeful. But I can't find my older profiles in C:\Users\Me\AddData\Roaming\Mozilla\Firefox except the one that was created today. But when I use Firefox to go to about:profiles I see 3 in there (1 being presently used). So something deleted the profile I was using yesterday. I certainly didn't. The error message says, "Your Firefox profile cannot be loaded. It may be missing or inaccessible." Well it obviously loaded fine yesterday. All I'm concerned with are my passwords really. Loading them up again will take an awfully long time.

I used a search program to search for the profile name but it didn't find anything anywhere. I searched both drives I use. I manually looked in both the Local and Roaming folders and both have just the one created today. Nothing relevant is in the Recycling Bin. Not sure what else I can do. They've vanished. Why would they show up in About:Profiles if they're not in either the Local or Roaming Users folder?

Look on your desktop. Do you see a folder called; Old Firefox? Look inside.

Yes I see it. Did the update move the old profile to this new folder on my desktop?

Sometimes, Firefox detects a problem and will create a new profile.

That must have been what happened. Thank you very much. Now I can just copy and paste anything I need over. Nothing like a fresh start.

I edited my original post to calm it down. It was a little hyper.  :)

Glad to help. Safe Surfing.