Have a look at this post:
Mame4all-pi with PS3 Controller
If you’re using retropi v2 and above the new locations for those files will be in /opt/retropie/emulators/mame4all-pi
If you don’t have the src folder, install mame4all from src using the retropi installer script which you can find in ~/RetroPie-Setup/retropie_setup.sh
