Are you trying to from this archive, or did you receive it as part of a software installation ?
Only open the file if you recognize the sender or the website from which it was downloaded. MM_19.7z
Since Windows and macOS do not always support .7z files natively, you will need a third-party tool: Are you trying to from this archive, or
While the exact contents depend on where you got the file, "MM_19" is a common shorthand in specific technical fields: MM_19.7z