Have an old Dell DVD drive from a laptop [Model DS-R2102] Would like to use it for a spare external drive. There is the connector port in the back that was meant to join to the circuitry in the drive bay. Is there some adapter cable that would allow power/data to be transmitted?

Don't know the exact model but all IDE type drives have two cables to them. One is teh voltage supply (a small connector with four pions in a white plastic ploug. this gets its supply from the power supply of the computer internally.
The other cable is a datra cable that connects (with 40 or so pins) and is a flat cable between the drive and a slot on the motherboard.

If you want to use the DVD as an external the best way is to buy an adapter box (not expensive) that has the cables inside it to accept and IDE type drive and has a mains plug (to give the box and dive power) and then it has an USB in/out cable that just plugs into the USB port.
This works well and can also be used to test IDE hard disk drives.