Need my Cairo station model converted/put into gmod

Ive got a Cairo station model with a frigate my buddy made attached to it. I did it in sketch up, but i cant convert it to .3ds, and thus cant covert it to .mdl. On top of all this, I’ve never even added a model of my own to gmod. I need it converted so i can put it in gmod, and upload it to gmod.org. I give credit to everyone who helps.I ll do anything i can to help, but like i said, im a bit of a noob at this,lol.Ill take requests after its converted(I love doin halo models). Good luck and Thanks!

oh and here’s the link http://www.filefront.com/14763611/Cairo.rar