A strong electrolyte is a solute that completely, or almost completely, ionizes or dissociates in a solution. Therefore, NiCl3 dissociates into ions completely. The dissociatio equation would be:
NiCl3 ---> Ni3+ + 3Cl-1
Threfore, the concentration of the ions would be 0.4 M Ni3+ and 1.2 M Cl-1.