Hello, do you want to make your own cable?
Serial cables are standard 9 pins. You are better off finding one ready rather than making one. You may need to look at http://www.langleydistribution.co.uk/support/wp-content/uploads/2016/06/Digi-782-Connect-To-IcrTouch-Guide.pdf to see how to set up port.
Wiring diagram
Male side of cable. Female side need some wires to cross pins.