Units

[menggong2005]

I have imported a 3D dwg file from AutoCAD into Revit for my site contour. The problem is that this dwg file was initially improted from ArcGIS into AutoCAD and the unit was set to meters. I have already started modelling my building in Revit in mm and am hoping to merge the two files into one.
Just wondering how I can do this? I am hoping to work in mm if it is possible...

Cheers