/data/data/org.mozilla.firefox is the directory in which Firefox's data is stored on Android. Where are Firefox's extensions' settings and data stored in there? The best I can tell is that they're going to be stored under /data/data/org.mozilla.firefox/files/mozilla/${profile}.default since the names for everything outside of that folder appears to be for temporary files, the application's cache, and network-related things.
These are the paths that I'm sure do not contain extension data or that I'm sure do contain ALL of the extension data:
/data/data/org.mozilla.firefox/files/mozilla/${profile}.default/browser-extension-data