R44s have US NATO sockets. (There are two types of NATOs - Euro and US).
You should be able to get converter leads from a place like flightstore or any other decent pilot shop.
Not certain about your DCs. Getting a mid-priced proper helicopter ANR headset like the Peltor might be wise. No converter leads needed - very comfortable and robust. Other than the v expensive Bose, Peltor seems to be the headset of choice in most 44s.
You say you have a pair of DCs. So what will the other two seats in the 44 get ?