Please explain the problem in detail. What happens? What is the exact error messages?

HI, if you used a Utility to Clean Windows such as CCleaner it may have deleted them. Did you Refresh Firefox ? If so the bookmarks are in a folder on your Desktop called OldFirefoxProfile. If not a new Profile may have somehow been created if it was corrupted please check here for 2 Profiles. The one you want is the oldest dated one. *https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data In Files : *bookmarks and history: places.sqlite *bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder If it is found shutdown Firefox to work on files. *https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks *https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile