The easiest way to decompress the file that I know of is with stuffit
expander. If you don't have it on your computer, you can download it for free:
To get the program, you need to give an e-mail address, but you can then
immediately opt out of further e-mails (which is what I did).
You should be able to drag the Milan file icon to the stuffit expander icon
and it will decompress it. If it doesn't then perhaps brighter minds than
mine will have to explain what happened. I hope this helps (and that it works)!
All the best,