I would like to know if a DS3 card used for a 7200 router will work on a 3600 router?
3600 series routers use the NM (Network Module) series of interface cards as well as the WIC (WAN Interface Card) Series.
7200 series routers use PA (Port Adapter) interface modules. They are not compatible physically nor electronically.
I'm afraid the 7200 series port adapters cannot be installed in 3600 series. They have different dimensions.