You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data. Note that best is to avoid copying a full profile folder.

You can use the button on the "Help -> More Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page (Root directory).

• Help -> More Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

Location used for the main profile with the random name that keeps your personal data (Root Directory on about:profiles).

• C:\Users\<user>\AppData\Roaming\Mozilla\Firefox\Profiles\xxxxxxxx.default-release

Note that "AppData" is a hidden folder.

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager
  key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db
• cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

Thanks, but the problem is "upstream" of your answer. I am trying to recover my bookmarks from a backup copy of information saved from a computer that no longer works. I can't copy the profile data from a Western Digital "My Passport" hard drive. Once I can do that, then I can do what you recommend. I'm hoping that someone can reply with a recommendation as to how to get my Firefox profiles off the WD drive.

Is this an external drive as I also have such WD drives and they connect via USB ? If this in not a normal backup, but is made by special backup software then you may have to install this software on the new device. It is possible that this backup software is stored on the drive in a special folder, so maybe look for that.

Yes, it's a USB drive. They recommended installing their latest software, which I did. It enabled me to point to the files I wanted, but was unable to recover them.

This is not a Firefox problem (not yet, anyway). It's a WD software problem. If I can just get the files off the (alleged) backup, I'm sure Firefox can use 'em. Thanks for your help, but until someone hopefully replies with help using the backup drive, it remains a WD problem, not yours.

...anybody out there have the same problem?

I think that best is to take this to WD support since this is a problem with their software. We won't be able to help you beyond the suggestion on how to copy files from a backup to a Firefox profile folder. Feel free to come back here once you have fixed the problems with the WD backup software and still have questions.