obj to 3d conversion is certainly searched by users that want to export 3D content, but to what format exactly is uncertainly. Hundreds of different '3d' graphics formats exist, so you have to refine your search and specify exactly what 3D format you had in mind.
It is true that some file types use .3d extension and some are even 3D models, but this is just a very narrow file conversion, in most cases to legacy formats. Some of these ancient formats might still be supported in dedicated 3D model converters.
Updated: October 13, 2023