Typically aftermarket comps screw on to an extended barrel that has been threaded, although STI truebore are all 1 price and SV push the comp on using a press and a very cold barrel.
3 or 4 chambers is the norm but there also may be side ports for stability.
Many current designs use hybrid ports in the barrel for maximum reduction
of muzzle filp as well.
You will need a new barrel to put a comp on a Para unlees the slide is shortened, this is a job for a competent gunsmith. although kits
are sold by Brownell's ( see them on the web) just not sold to Canada.
I would suggest selling the Para and buying a comped STI or SV in 38 or 9 mm
before wasting a lot of time and money with modifying a Para.