how do i convert 3d mesh to 3d solids? 

Hey aTURTLE01,
I use AutoCAD Architecture 2008. To convert 3d meshes to 3d solids is quite easy. You need to have the massing tool bar open, ( if you don't, go in to the content browser, under stock tool catalog choose modeling tools and then 3d solids. Drag the 3d solids tool bar and drop it in the tool pallets). Select the Convert To Mass Element Tool, and follow the directions.
Hope that helps,
nameci