Here are two ways (one long and one short 🙂 ) to find out the Linux Mint or Ubuntu release information of your system :
The long way :
1. Go to Menu > Administration > System Monitor
2. Click on the System tab, below that will be the version number and codename.
The short way :
1. Launch Terminal and type : lsb_release -a
This too will display the same thing.
Cheers.