Thank you for posting to Fixya.com and it is my pleasure to guide you.
To help you in the furture I have found the manual for reference. Click the link or copy paste it to download it. http://www.posguys.com/download/iDP3550UME_09E.pdf
From the manual for the Interface Cables, the manual has pictures.
4.2 Connecting the Interface Cable
1. Turn off the power. (Mating side included)
2. Check the top and bottom of the cable terminals, and connect to the interface connector.
3. Secure the cable terminals.
Serial interface: Tighten screws to secure.
Parallel interface : Turn clamps to secure.
4. Connect the interface cable to the computer.
4.3 Connecting the Drawer Kick-Out Connector
1. Turn off the power.
2. Check the top and bottom of the drawer kick-out cable connector and connect it to the drawer kick-out connector located at the lower section of the printer.
3. Screw the grounding cable of the drawer to the grounding terminal located at the lower section of the printer.
CAUTION: • Connect only the prescribed drawer (Solenoid) to the drawer kick -out connector.
Good luck and please post back that you are successful and give thumbs up if my solution has worked for you. If I can be more helpful just reply.