You should be able to download the field cad from the competition overview page, or any other CAD model from the vexrobotics website as a .step file, which most cad softwares should be able to use
https://www.autodesk.com/products/fusion-360/blog/import-step-file-into-fusion-360/
It might be easier to use the Fusion 360 Parts Library to import parts instead of downloading them individually from the website!