First off all I hace to say that English is not my firs language so I hope you can understand me.
I just put together all the "pieces " of the patrol car that comes in "modern vehicles 2" package. 
Now I what to create a single prop from all those pieces and save it as "patrol car", so the next time I need to use it, I don't have to put all the pieces together again to create the car patrol.

Thanks in advance and excuse my terrible english.