You can, simply open up the Bookmarks menu, click on 'Organize Bookmarks', then click on 'Import and Backup', followed by clicking 'Backup'. Chose where you want to save this backup (possibly your desktop), and then update your version at will.

If by misfortune you lose all of your bookmarks, simply open the Bookmarks menu, click on 'Organize Bookmarks', then once again click on 'Import and Backup', but click on the 'Restore' button. Click on 'Chose file...' and browse to the backup file.

If you lose bookmarks with an update then a possible cause is a problem with the file places.sqlite that stores the bookmarks and the history.

• http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox

I saved the files as suggested & they are in Json file & the computer says unable to open this file as not known ????????

You do not open a JSON backup, but you restore such a backup in the Bookmarks Manager (Library; Bookmarks > Show All Bookmarks). Also make sure that the file has a .json file extension.

• http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox