You can open the dwg file as an Object, then save it as an Object, the 2D elements will be converted to 3D (as planar elements). This object can then be placed in the project file as a 3D reference.
David
David Maudlin / Architect www.davidmaudlin.com Digital Architecture AC27 USA • iMac 27" 4.0GHz Quad-core i7 OSX11 | 24 gb ram • MacBook Pro M3 Pro | 36 gb ram OSX14
I think this article can help you. In the first steps it talks about saving ArchiCAD content as DWG, but from that point the steps are the same as in your case: