If this milling center works the same as the vast majority of similar machines, it won't be able to accept 3D models directly from a CAD design package; it needs them to be processed through CAM software that takes into account things like the tools you plan to use, the size of the workpiece, the depth of cut and spacing of tool passes. The generic G-code this software generates is then run through a post-processor or "post" for short, that customizes it to the particular way your machine wants it presented. So you can use pretty much any CAD software to design your model, you just need to find a CAM package with a "post" for your machine. We sell a product called VisualCADCAM 2020 (aka VisualMill) that comes with a wide variety of posts for different machines. If your mill isn't on the list, Mecsoft will furnish one for free; you just have to provide a sample of code that works on your machine. Other CAM software companies charge for this, so if you're shopping around, ask about the cost for configuring a custom post in order to get an accurate total price.