I think he want's to covert his FAA CPL/ME/IR to a JAR license if i didn't got him wrong..
In america to take your CPL you just have to complete a single exam, same applies to an FAA ATPL writen exam. That is the huge difference between EU and USA when it comes to the theory part not to mention other things.
That said he would have to take the CPL exams in EU which are 9 if my my memory doesn't fail or take the 14 exams if he wants an ATPL frozen.
Flight time to convert will also depend on the amount of hours that they (JAR state) will credit for his experience. The more hours he/she has the better, then more credit given = less it will cost
Hope it helps if this was what you where looking for.