Have a SIG 250C-- anyone know where or tif I can put a 9mm barrel in it, and whether or not the current magazines wiki work with 9MM ??? THANKS

You won't be able to simply drop in a factory 9mm barrel. It won't work with your non-9mm slide, recoil spring, and magazine.

Barsto offers (or used to offer) a conversion barrel to convert a Full Size .40 P250/P320 to 9mm, but that's only for the Full Size pistols, and I believe that item may be discontinued anyway.

If you can find one, you could buy one of the old Sig factory P250C 9mm X-Change kits, which will contain a 9mm slide, barrel, recoil spring, and magazine. But those are also discontinued, so you'd have to stumble across one on the secondary market.

Unfortunately, since the P250 was discontinued several years ago, and wasn't much of a hit at the time anyway, there's not much aftermarket support for it.