I recommended a program like KeePass password manager. There it can creates logins and password and link to those login in a secure file rather then doing what your doing has chances to loose or misplace logins. This program can be used as a USB drive to open your logins and URL and passwords to your sites rather then having to use html saves as that can be tricky to load and see your logins and sites.

See also:

• https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
• https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them
• https://support.mozilla.org/en-US/kb/export-login-data-firefox

You can copy certain files with Firefox closed from another profile folder to backup your personal data. Note that best is to avoid restoring a full profile folder and only restore important files that are safe to restore/transfer.

• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins) and key4.db (decryption key and primary password) for logins saved in the Password Manager
• cert9.db for certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

Thank you cor-el and dropa. Your replies are most helpful. I'm very grateful for you taking the time and trouble to explain the solution to my dilemma. Thanks again.