I suggest creating a backup in two formats, and you can store them off your hard drive, for example, on a USB flash drive, and/or in the cloud on DropBox or OneDrive or Google Drive, and/or you could attach the files to an email message and mail them to yourself.

Backup Format: Restore bookmarks from backup or move them to another computer (ignore the part about restoring for now)

Export Format: Export Firefox bookmarks to an HTML file to back up or transfer bookmarks (this format doesn't save tags you may have added to your bookmarks, but it's cross-browser compatible)

Did you want to save any other data? For that, see: Back up and restore information in Firefox profiles.

These add-ons can be a great help by backing up and restoring Firefox

FEBE (Firefox Environment Backup Extension) {web link} FEBE allows you to quickly and easily backup your Firefox extensions, history, passwords, and more. In fact, it goes beyond just backing up -- It will actually rebuild your saved files individually into installable .xpi files. It will also make backups of files that you choose.

OPIE {web link} Import/Export extension preferences

Thank you so much; however, I am an inexperienced senior citizen. If I create a sync account, will that automatically save the bookmarks for me?

If you create a Firefox Account and set up Sync, it's very likely that Firefox will include your bookmarks among the data it saves on the Sync server. And you can use the Options page to see what categories are selected.

However, I'm not sure how quickly that happens, so I'm not sure how soon you could be confident that your data is saved on Mozilla's servers and it's safe to erase your local copy. Hopefully someone else can answer that.

Are you backing up anything else on your computer?

DO NOT use Sync as a backup medium!

If all you want is your Firefox Bookmarks using FEBE or OPIE is overkill for your needs, IMO.

Export in HTML format, saving to a removal Flash Stick, and then Import from HTML is all you need to do. https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Yes, technically Sync would work, but we have seen way too many bad experiences posted in this forum by users who incorrectly used Sync to "backup" their Firefox data using Sync. The users who may have used Sync successfully typically don't post here and say that it worked.

Sync is only intended to be used to synchronized Firefox data across multiple devices. The Sync server isn't intended for storage of the only copy of a users Firefox data; that data us wiped with merely changing the Account Password, and that is due to that Password having been used to create the dual encryption keys for that data. Change the Password and the old "dual keys" won't decrypt that data, making that data useless and it is deleted when the Password is changed.

Plus that feature allows the user to clear corrupt data from the Sync server without needing to start all over again with a new Sync Account with a different Password. And before that feature was added I went thru 7 or 8 different email addresses while testing the earlier version of Sync 1.1 that was used in the Firefox 4.0 up thru Firefox 28.0 versions. IMO, a "stroke of genius" by adding that feature.