Mac 3D Model Split Tutorial

I have an STL file that simply needs a perfectly vertical cut so the model becomes two equal halves. I’m on macOS and, as a complete beginner, I haven’t installed any 3D software yet. What I need is an... (Budget: $10 - $30 USD, Jobs: 3D Design, 3D Graphic Design, 3D Modelling, 3D Printing, 3D Rendering, Blender, Mac OS, Unity 3D)