ls -l ~/Library/Application\ Support/Firefox/Profiles
.
(you need to put a backslash before the space in the directory path)$ ls -l ~/Library/Application\ Support/Firefox/Profiles total 0 drwx------ 53 jasmith1 ABC\Domain Users 1802 Jan 23 11:56 bgq13udo.default $
Within that directory, you will see files such as the following ones:
$ ls ~/Library/Application\ Support/Firefox/Profiles/bgq13udo.default/ SiteSecurityServiceState.txt key3.db addons.json localstore.rdf blocklist.xml logins.json bookmarkbackups mimeTypes.rdf cert8.db minidumps cert_override.txt permissions.sqlite compatibility.ini places.sqlite content-prefs.sqlite places.sqlite-shm cookies.sqlite places.sqlite-wal cookies.sqlite-shm pluginreg.dat cookies.sqlite-wal prefs.js crashes revocations.txt datareporting saved-telemetry-pings evernote_native.bin search.json extensions search.json.mozlz4 extensions.ini secmod.db extensions.json sessionCheckpoints.json formhistory.sqlite sessionstore-backups gmp storage gmp-gmpopenh264 times.json healthreport webapps healthreport.sqlite webappsstore.sqlite healthreport.sqlite-shm webappsstore.sqlite-shm healthreport.sqlite-wal webappsstore.sqlite-wal jetpack xulstore.json $
Alternatively, the steps below can be used to open that profile folder from within the Firefox browser itself.
You will then see a Finder window showing the contents of the Firefox profile folder.
Note: the steps and screen shots above are for Firefox ESR 45.6.0 on an OS X system, but should be similar for other versions of Firefox, at least versions of Firefox close in time to this version.