I rebuilt it in 3ds Max. You'd have modeled it the same way in Blender if you had used it. Both are surface or mesh modelers. Then I exported both an .stl and .obj version for you. This design might have just as easily been modeled in a CAD program like SolidWorks (insanely expensive) or IronCAD (expensive but reasonable). Both are expensive but there are some lower cost and at least one free open-source CAD program out there. They are parametric modelers and are called 'solid' modelers. It's sometimes easier to model non-organic objects in these CAD programs and because of the parametric nature of them, it's quite easy to modify dimensional requirements if those change.

I'd try FreeCAD (steep learning curve), Meshmixer (easy) and Blender (steepest learning curve but you get animation). These are all free.

If you are a student, the supercharged CAD programs are all really affordable. I'd love to get my hands on a student version of Solidworks. It's about $8500 for a commercial license and I think it's only a few hundred for the student version.

If you are going to really put your 3d printer to work, it's critical that you are able to do some good modeling. Otherwise you are at the mercy of Thingiverse, etc. There's a lot there but not everything. And besides, once you print your phone case or a few super hero characters downloaded from there, you need to move on...lol....well, unless you want the Itty Bitty double extruder by our user "clough42.' It's one of the best things on Thingiverse...(how's that for a plug clough42?)