Conversion of obj files to 3dm file format

It looks like obj to 3dm conversion is some sort of 3D object conversion and as such it can only be done using some 3D modeling tools or dedicated conversion utilities with support for both of these formats. Several 3D modeling tools can be used for this and you can even find some dedication, web-based online converters.

Open OBJ file    Open 3DM file

Related software

AccuTrans 3D

A CAD 3D geometry translation software

Autoconverter

A converter for 3D formats

Autodesk Fusion 360

3D CAD/CAM tool for product development

Babel3D

An online CAD conversion service

PolyTrans|CAD+DCC

A 3D CAD translation software