where does the firefox-bookmark store at?
 

I wanna backup those information. but don't know where does the store. please tell the directory. thanks.

in your home directory under .mozilla and some distros might put it under .firefox. Thos dot files are hidden directory so you will need to back the directory up from the command line.

cp -r .mozilla/ /path/you/want/tosave/to

On my ubuntu machine, the firefox bookmarks are in:
/home/bs/.mozilla/firefox/fjprbdhv.default/bookmarks.html

On my slackware machine they are in basically the same place, except the randon chracters on the .default are different:
/home/bs/.mozilla/firefox/v76ng9qc.default/bookmarks.html

worth updating this info ...
 

Mine is in:

~/.mozilla/firefox/<some random string>.default/bookmarkbackups/bookmarks-yyyy-mm-dd.json

Firefox has a routine to export and import bookmarks. On the menu bar:

Bookmarks-->Show All Bookmarks-->Import and Export.