Not being au fait with the Austria's CAA, I only can give you the UK CAA's reference. Try
LASORS.
It's a free download.
The main thing to remember is you can only convert "like for like". So if you have an FAA CPL, you can only convert it to a JAA CPL.
Of course you'll have to do the 14 wonderful JAA ATPL subjects first so you can "convert" the IR.