According to this 2014 500L Owner's Manual "the proper cold tire inflation pressure is listed on the driver’s side B-Pillar or the rear edge of the driver’s side door" - however I'm guessing there's nothing there on yours? That manual is on Fiat's US site so maybe things are different over here for some reason.
If you just need the values they are on page 258 of the 500L Handbook here.