3D STL to STEP Conversion

I need a 3D STL file of an artistic piece converted to a STEP file. The model requires minor adjustments, specifically modifications to thickness.

Ideal skills and experience:
- Proficiency in 3D modeling software
- Experience with STL and STEP file formats
- Ability to make precise adjustments to 3D models
- Attention to detail and quality

Please provide samples of similar work done.