Autodesk has a free program called DWG TrueView. You can look at or print CAD files, but will not have the ability to modify the files. You willhave the ability to save the DWG down to an older CAD format. I typically save CAD files back to Version 2000, which is the most recent version that M8 or M9 will read.
That said, CAD files (at least from my experience) will have hundreds of unnecessary layers, blocks, and other leftover bits. They often have internal errors that can also cause troubles. I usually use other AutoCAD-like programs to clean and repair files before saving them down to Version 2000. I am currently using a free version of Draftsight, which will no longer be free as of January 2020. Another program I have not played much with is FreeCAD; an open source CAD program. Winnowing down the number of unnecessary, empty layers, blocks, and formats greatly helps in reducing the sheer number of choices of layers to import. Having DWG TrueView, Draftsight, or FreeCAD running on a second monitor also helps to narrow down which layers contain the information you need to import.
Best of luck with the import.