Yes, 3d slicer can create stls.

These might not be good enough for modeling, you might have to repair them, e.g., with autodesk meshmixer and you might need to mesh the repaired stl files with some other software (tetgen, for example).

Thank you very much for your answer!

Isn't it possible to do the meshing with Abaqus?

Abaqus itself cannot read stls as solids (it interprets them as surfaces), you need to convert to iges or similar to mesh it in Abaqus. Depending on the geometry, the ABaqus mesh may be worse than what tetgen can do