: Download and install a compatible archiver like the official 7-Zip or WinRAR .
: Ensure all numbered segments (M20CH03.7z.001, M20CH03.7z.002, etc.) are in the same folder . M20CH03.7z.001
You can use 7-Zip on any computer, including a computer in a commercial organization. You don't need to register or pay for 7-Zip. How to Open and Extract .001 Files - Microsoft Q&A : Download and install a compatible archiver like