To import bookmarks from another browser or from a file in HTML format, open the library by choosing from the menu bar, Bookmarks › Show All Bookmarks. To start the Import Wizard, click Import and Backup › Import Bookmarks from HTML and choose an import location. Start the import by clicking Next. Imports from an HTML file are imported as is.
Exporting bookmarks is also done via Import and Backup in the library window. To save your bookmarks as an HTML file, choose Export Boomarks to HTML. To create a backup of your bookmarks, choose Backup. Firefox uses a JavaScript Object Notation file format (.json) for backups.
To restore a bookmark backup, click Import and Backup › Restore. Then locate the backup you want to restore from.