You're concerned over those Firefox.exe entries showing in Task Manager at the Details tab...?...

(1) Is that right after a reboot? (The equivalent of a reboot is click Power, then Shift+Shutdown. The next time you turn on your computer, you will have rebooted.) If it wasn't a reboot (just a regular Shutdown), then it was a hybrid that stores the session onto the HDD. It would be reloaded at boot with those Firefox.exe's still loaded.
(2) Did you search for Firefox.exe in Autoruns? Put it into the search box. Widen the columns using the divider lines in the Header to spot it, if found.
I'm thinking, if you don't find it in Autoruns, then you are seeing it in Task Manager because of the hybrid Shutdown. You must have run Firefox which loaded them, then did a hybrid Shutdown instead of a Restart.
And I spotted this in one of your pictures...

Widen that column so we can see what is loading.