If you have DAZ installed, its easy!

Open Studio, search for the scene, Click on the little box at the right side of content library, a panel opens, select “Create Poser Companion Files” and click on it, the next panel opens where you can select where your scene or whatever you want to convert should go, for a scene, use under “Use this library and file extension”  and select “Scene” then click on “Accept” Studio will convert the scene.

Open Poser go to” Scene” look for DSON conversions and search for your Converted scene, open the scene and save the Scene as poser scene, I think than you can open it with Poser 12.

 I don’t have poser 11 or 12, but with poser 2014 it works fine for me, before I switched completely to studio itself!

There are a lot of scenes with instances that don`t convert very well! Studio has a script tool that convert instances to objects, but after conversion the scenery is very poly heavy in Poser (you have to buy this scrip)