I have some files that have been created in another piece of software of 3D objects. When I import them into Civil they come in as an 'ACAD_PROXY_ENTITY'. They are in the form of a 3D object, just seperate entities

Does anyone know if it's possible to convert them back to a 3D object i.e. Solid or mesh. I also want to use them in 3Ds Max but can't as the form they are in?

Any help greatly appreciated

Thanks
James