You generally don't, because Exchange is pretty tightly integrated with Active Directory.
"Restoring" the whole system to a test site either means that it's not going to work, or it's going to run the risk of messing up whatever existing Active Directory forest you restore it into. (Or both. Probably both.)
What you should do, since you're only wanting to check the mail databases is to restore the mail database to the recovery database (RDB) on an existing Exchange 2010 server. The precise process varies based on what specific backup software you're using (which you haven't revealed), based on the fact that native Exchange server support for backups and restores (which are pretty basic and ought to be pretty simple actions) is rather poor, as is the existing Microsoft documentation.
Given that, here's a short guide on how to create a new recovery database, not from Microsoft. Using Exchange Management Shell, it's:
new-mailboxdatabase –recovery –name [databasename] –server [servername] –edbfilepath [pathtodatabase] –logfolderpath [pathtologfiles]
Assuming you don't have a way to take the database backup in the first place, here's a guide on how to do it for free, using Windows Backup Server.
I'm also going to link this guide, which has a basic run-down of how to actually use the RDB once you've populated it with your backup database.