Trying to navigate the Lionel parts site has gotten more complicated with all the advances in technology: So many more parts and product variations.
I don't know if you are actually in France: Most likely you'll have to mail order the parts. Most Lionel parts dealers would probably have these items in stock also. You're going to need a soldering gun and the skills to use it, to solder the wires to the pick up, which does take a little skill as you don't want to melt the plastic on the pick up assembly.
I have no idea whether Lionel makes that part with wires already soldered on to it. I know K-Line at one time did.
Anyways, you'll need a pick-up assembly made for plastic trucks, which is here, part 10 in the list:
But then you'll need the bulb fixture and an 18 volt bulb made for the LionChief power set up, items 7 and 8 on the list. Disregard everything else in the picture as they are diecast trucks instead of the plastic ones you have.