Originally Posted by
damulta
Thats the bottom bracket and you'll need to change that in order to put new cranks on. Your bike is french and has a french threaded bottom bracket for which there are very limited options. That Velo Orange bottom bracket in that link is basically the only option. Once you replace the bottom bracket you can put just about any modern crank on provided it fits a "Square Taper" spindle.
you need to order the Bottom Bracket in the correct length. That's dependent on your cranks. Pick out your cranks and that will give you the Bottom Bracket length to order.
I agree with the above posters, leave it alone and just ride it. Get something better to spend money on.