To convert your FAA CPL IR into JAR ATPL you need:
Read through 14 books, then pass 14 exams with 80% passrate (1 exam for each subject).
You can do it on your own, distance learning (2000$) or 6 months classroom (6000$).
All exams, if you pass them on 1st attemt, will cost you 1200$.
Now, once you done with that, you gonna have to do some flying and pass couple of practical exams.
How many flight hours you need, depends on how many hours you have.
But in total, you gonna have at least 200hours.
So, if you havent done anything, you should count 7-9 months and around 10-15.000$ to get your JAR ATPL