This is an essential part of your setup.
This is the Standard sensor cable with 2 mm banana connectors for WE, WE sense, CE, RE and ground including crocodile clips (red, black, blue and green) with a connector (Type LEMO) to your potentiostat. This cable is usually included in the purchase of an EmStat3+.
A LEMO and a TRIAD plug or receptacle are easy to differentiate, since the TRIAD plug has a screw thread.
The EmStat3+ needs this LEMO plug with 4 pins. This is also valid for the MultiEmStats containing EmStat3+ boards.