a quicker way might be to switch to a libretro (retroarch) emulator for mame. eg, if you are currently using mame4all-pi, you could switch to lr-imame4all which is retroarch (so will be automatically configured), and also runs on the same romset so should work much the same way. you switch default emulators via: https://github.com/RetroPie/RetroPie-Setup/wiki/runcommand
I managed to swap emulators thanks to your advice (thanks) and the Playstation controlled detected logo came up
But suddenly the keyboard didn’t work and the “insert coin” was still assigned to key 5 on the keyboard so I wasn’t able to add credit (key 5) or access a game (key 1) – how might i associate these to PSx buttons?