The file that specifies the emulator to run is
/etc/emulationstation/es_systems.cfg
If you navigate there and edit it with
sudo nano es_systems.cfg
you will scroll to the MAME section, and you’ll see which it is using, often of it isnt set to mame4all already, the mame4all option would be there but commented out, so its easy to enable it.
But as Roo says, much better idea to use a newer image.