Find the profile that you want to install. Then;

When you are ready, we can start moving parts of your old data and Copy it to the new profile.

First; open your file browser to the New profile;

Type about:support<enter> in the address bar.

Under the page logo on the left side, you will see Application Basics. Under this find Profile Folder. To its right press the button Show Folder. This will open your file browser to the current Firefox profile. Now Close Firefox.

Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder

Linux: Under the page logo on the left side, you will see Application Basics. Under this find Profile Directory. To its right press the button Open Directory.

Second, open another file browser to the Old profile.

Warning ! ! Only Copy the files you are told. We will avoid anything that might cause problems. Here is the list of files;

cookies: cookies.sqlite Do not bother. Cookies will be created when you return to the website. However, you will have to log in everywhere. And you may lose any settings that websites store on your computer.

extensions(add-ons, themes): it would be better to download them fresh. If you need to remember what add-ons you had, open the extensions sub-folder and look at the .xpi files

logins.json and key3.db [v58+]key4.db : These are the password files. Copy Both !

persdict.dat : custom dictionary - words you added to the dictionary

mimeTypes.rdf [v55+]handlers.json : What to do with what type of file.

places.sqlite : History and Bookmarks.

prefs.js : Your settings. Note: If you were having problems, this could be contaminated.

cert8.db [v58+]cert9.db and possibly cert_override.txt : Stores all your security certificate settings and any SSL certificates you have imported into Firefox. If removed, the cert8.db, cert9.db file will be replaced.

search.json.mozlz4 : file stores the user-installed search engines that are available in the Firefox v47+

search.sqlite file and searchplugins folder store the search engines that are available in the Firefox Search bar before Firefox v47

Copy these files from the old to the new. You may get a message that the files already exist. Choose to over-write for each file.

Can you explain when I am in 'the old profile' and when I'm in 'the new profile,' and how to open the browser to 'the new profile?' I have no idea when each is present, the old or the new. Secondly, I got no notification to indicate which files I should/shouldn't copy and paste. Anyway I copied all the profile files into the only profile folder indicated after . It didn't make any difference. Still no bookmarks showing. Please advise.

Also can you explain, 'open another file browser to the old profile?' Safari? Chrome? Again, how do I know they are in 'the old profile?' And then what is there in another browser to indicate I should copy various files into wherever? Confused!

Do you still see/have that folder you created on the desktop with the back up? Or is the problem you are having is that you can no longer find it after repairing/upgrading your o.s.?

Yes. I have the folder with all the files in

ok, so do you also have a functional FF installation running and operational?

definitely

hmm? sounds like you are on the right track!

ok, so its just a matter of opening up the folders of both profiles and copying 1 or 2 files from the back up and into the new one

here is a link to an instructional webpage. but you can also google for them too:

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

if you are successful with building your new profile via the old data, please let us know so we can give you the next steps for a better methodology in preserving your data.