You do need the path to Plex SQLite, which, for truenas, is not mentioned in the support document.
However, Plex SQLite is in the same directory as the Plex Media Server executable.
Also, the path to the PMS executable is listed at the top of the Plex Media Server.log file (at least on Windows & Linux).
I looked at a set of logs from the server-truenas section.
It references /usr/local/share/plexmediaserver-plexpass/Plex_Media_Server.
So, you might check that location and see if it has the Plex SQLite executable.
