ISO STP/STEP product data files are widely supported in various CAD software and so it is highly probably that those with support for Inventor formats can convert STP to IPT. The most obvious choice here would be Inventor itself of course.
Convert ISO-10303 STEP product data to AutoDesk Inventor CAD part.
We found 2 software records in the database related to .stp to .ipt file format conversion.
Microsoft Windows software - convert stp to ipt on Windows
Autodesk Inventor is modeling application used to create 3D digital prototypes.
Convert from stp 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 stp to ipt. 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 2D and 3D CAD construction software