The external M-codes of the 18i era were either M50~M53 or M91~M94
You can search you ladder for those to see how it is being used, and what I/O it connects to, from that you can trace the wiring from the I/O to confirm it is working.
Finding the M-code and checking the status of Keep relays associated with the barfeed (K7.0~K7.5?) Should let you track whichever bit is active to see what the ladder requires.
Any program that any end user would supply for a machine of that time, would be a shot-in-the-dark, and has just as much chance of not-working on your machine...and wasting your time...