Do you have a C:\Windows.old folder ?

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.

• 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 so much, cor-el! This is far more detailed info than I've seen anywhere. I'll be experimenting with this as soon as possible.

So, could you please break this down into steps, with as much detail as possible and even images, if you could? I'm not too tech-savvy. I did find my C: Windows\old folder. Am I supposed to be able to find the above bulleted items in there? None of them are. I also don't know what or where the "current profile folder" is--is this something in Windows, or in Firefox? I guess the former, since I'm supposed to access it while Firefox is closed? And is C: Windows\old a profile folder, with the idea being not to copy the whole thing but instead copy each of its contents individually (assuming I had them, which I don't)?

I'm also still interested to know whether if it makes a difference whether I had the same Firefox version before and after the Windows refresh. Thanks and sorry for the learning curve.

First, make sure Windows shows you hidden files and folders. This article has the steps for that setting: https://support.microsoft.com/en-us/windows/show-hidden-files-0320fe58-0117-fd59-6851-9b7f9840fdb2

Next, explore up this path:

C:\Windows.old\Users\<username>\AppData\Roaming\Mozilla\Firefox\Profiles

At that point, you should find one or more profile folders.

You can re-use a same-version or previous-version folder, and the same-version or newer-version Firefox should be fine with that. The only glitch would be if you changed your Windows username, but assuming not, it should work.

Let me point you toward a thread with the specific steps for "transplanting" an old folder into your live Profiles folder of your running installation of Firefox so that Firefox will recognize and use it:

https://support.mozilla.org/questions/1321847

If that doesn't work, then copying individual files might be needed.

Thank you! Since I was pressed for time, I had my IT boyfriend (who was not familiar enough with Firefox to answer the above questions) take control of my computer remotely and use these instructions to focus on restoring my bookmarks. Using the methods described, he did find old bookmarks of mine in the location specified, but for some reason, the files were only for dates up to half a year ago. After my twice insisting that maybe there were more recently saved bookmarks somewhere else, he did a search in my C drive for bookmarks*.jsonlz4 (the elements of the file names that all the previously found bookmarks had in common, plus the * to search for items with any additional elements in between), and this search brought up the very last set of bookmarks that was created before the refresh. Success! From there, I was easily able to import the bookmarks back into Firefox.

It's great when Windows search works!