Creating a VTK file for region mesht/tet

hello,

I'm trying to insert particles in any region that you want, something like a custom region.

I was wondering if there is a software that can make a geometric figure and then export the file in VTK format for later use it as a mesh / tet in the region command.
Something similar when you make a figure using SolidWorks and then export the file in a stl format for use it as a mesh/surface.

Any suggestion or question will be greatly appreciated and I'm sure it will be considered.

Have a nice day,

zealakis.