Your best option for working and converting of .3ds files would be 3ds Max, previously known as 3D Studio Max. Formats from this programs are rarely supported in 3rd party apps in their latest versions, however some dedicated converters may still read them and allow export (or at least limited export) to other 3d modeling formats, including the STEP standard (.stp, .step).
Convert 3ds Max (3D Studio MAX) graphics to ISO-10303 STEP product data.
We have found 9 software records in our database eligible for .3ds to .stp file format conversion.
Microsoft Windows software - convert 3ds to stp on Windows
3D viewer and converter with huge file type support
Convert from 3ds file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned 3ds to stp. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A 3D model converter
Leading 2D and 3D CAD development software from Autodesk
A family of 2D/3D CAD software products for Windows
A widely-used 3D animation application from Autodesk
A converter for 3D formats
A CAD viewer program with conversion capabilities
Apple macOS / Mac OS X software - convert 3ds to stp on OS X
A 2D/3D CAD software for OS X
Mac version of popular Autodesk AutoCAD software