stp to sab conversion is most likely related to export of 3D models between STEP and 3D ACIS formats, something that should be certainly doable.
Most 3D modeling tools actually support import of STEP exchange format (.stp or .step), either directly or via plugin. What is less common is support saving to binary version of SAT format, but you can certainly find many software options for stp to sat conversion.
Updated: October 16, 2023