http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

jscher2000 has a tool on his website to extract out your bookmarks and save them to an HTML-format bookmark export file. If you want to try it, here is the page:

https://www.jeffersonscher.com/res/bookbackreader.html

To open the bookmarkbackups folder in Finder, use the "Open in Finder" button in the first table on the Troubleshooting Information page, and double- click into bookmarkbackups where you should see several dated files. From there you can drag and drop onto the conversion tool.

To import the HTML file, see the steps in this article: Import Bookmarks from an HTML file.

I have tried that website however I have had no luck, no .jsonlz4 to be found anywhere on my Mac, nor a bookmarksbackup folder. :(

Rupi said

no .jsonlz4 to be found anywhere on my Mac

If that is true, your data may be gone.

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

There is no Old Firefox folder :( Where would my data go and why? I can see the backups in the firefox bookmarks window, they just are not loading.

So I actually found some backup files on my computer (the seach didnt find them but I manually went into the bookmarkbackups directory. I dragged it into the website above to export as html, and even created a repaired .jsonlz4 on my desktop, however Firefox is still not loading or accepting these files.

If I open the html file in a browser, I can see my bookmarks are there somewhere in code.

From what Firefox version did you update?

If you updated from a very old Firefox version then your backup might not be compatible. This can happen with a JSON backup, but shouldn't happen with an HTML backup.

The System Details list shows that you have a very old Shockwave Flash 11.8 r800 version that hasn't been updated for years. You can download the latest NPAPI Flash plugin for Firefox on this page.

• https://get.adobe.com/flashplayer/otherversions/

OMG YES THANK YOU. I uninstalled Old flash player and reinstalled the new one and opened Firefox and the bookmarks etc everything is already there! THANK YOU SO MUCH! This fixed it!

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

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox

In Mac OS X v10.7 and later, the ~/Library folder in the Home directory is a hidden folder.

• http://kb.mozillazine.org/Show_hidden_files_and_folders#Mac_OS_X

If you use the Time Machine or other backup then try to restore file(s) from this backup.

• https://www.apple.com/support/timemachine/
• https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile