Please explain the problem in detail. What happens? What is/are the exact error message(s) ?
Restore Bookmark Backups
Firefox automatically makes backups of the bookmarks. These are stored in the bookmarkbackups folder.
Open the Bookmarks Manager; Press the Alt or F10 key to bring up the toolbar, and select Bookmarks. Hot key is <Control> (Mac=<Command>) <Shift> B. Firefox 84+ <Control> (Mac=<Command>) <Shift> O.
Once the window is open, at the top of the page, press the button labeled Import and Backup. Select Restore. From the list, pick the file you want and click it.
The backups are stored in a jsonlz4 file named something like this; bookmarks-2016-06-29_1424_enD1GTH ya0JmicnYWg4V4g==.jsonlz4
In this example; 2016-06-29 = date created, 1424 = number of entries.