You might be at a disadvantage as at this age the chances that your control is 'stock" are not that great.
The original had a I/O card installed into a ISA slot. This card had ribbon connectors to the hard drive and floppy and had a serial port and parallel port. The serial port had a plug and cable that went out to the "fire-wall" with a DB-25 connector.
Later machines had on board Com ports which also went to the electrical cabinet wall as a DB-25 connector.
If you are expecting a DB 9 you are mistaken.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)