Global Mapper v25.0

Projection/Scaling issue

I have some drone data that I captured using GCPs and additional check points and processed and exported in meters.
I have been sent a DWG from the client im think that it is in MM and need to match these files up. 
Q: How do I scale these files to match? I have tried changing the planar units and elevation units when I import but this doesn't fix it?