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 AC29 USA Perpetual • Mac mini M4 Pro OSX15 | 64 gb ram • MacBook Pro M3 Pro OSX14 | 36 gb ram
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: