Appdata is a hidden file, you will have to enable hidden files and folders perhaps to find it. http://www.bleepingcomputer.com/tutorials/how-to-see-hidden-files-in-windows/.

After you find the appdata folder, read https://support.mozilla.org/en-US/kb/Managing-profiles and Recovering important data from an old profile.

Roger that, hidden files are exposed. Still, when I go to the old drive I do not, cannot, see/find the appdata file on the old drive. Kinda stuck. Haven't installed any office programs, so I wasn't able to upload a picture of my Mozilla folder. Wonder what would happen if I simply copied the entire Firefox folder from my old drive to the new drive? Any ideas? And thanks for responding.

The Firefox folder inside program files doesn't have the Firefox profile data. So you say you go into Appdata, then Roaming, you aren't seeing a Mozilla folder?

Thanks. I found the Appdata file, and much of it has already been modified by Firefox, though I am looking at a bookmarks.json file from 3/19 which is about a week before the new build; I am thinking this should be it. I am on the West Coast, far northern Calif., and it is now about 10:10, and I have to quit working on this PC before my eyes burn out. I will check your referenced directions tomorrow and let you know of any progress/regress that I make. Thanks for your help. Please check this forum again tomorrow or over the weekend, I really do appreciate and need the help.

UPDATE: 3/31, 1040PDT. Thanks Tyler, your suggestions and information solved the problem. Following the information you provided and in the Firefox links you provided (and other links in those pages), I found my old profile and new profile. Saved both profiles to a USB flash dr. Then deleted the new profile and the profile.ini from my C drive folder and installed the old profile in its place. It worked. One note: I never saw anything about copying the profile.ini data from old to new folders, but without doing so any attempt to start Firefox Browser will give you a message that it is already running and to close it or restart the PC: It won't show up in Task Manager, and even shutting off the PC won't clear that message. Again, thanks a bunch. I have all my bookmarks and passwords back.

Firefox can't find a profile unless it is registered properly in profiles.ini, so you always need to copy that matching profiles.ini file as well or edit the existing file and add the profile data to it or use the Profile Manager to create a new profile and choose the location of that copied profile to make Firefox see that profile and use it.

• http://kb.mozillazine.org/Recovering_a_missing_profile