If you have forgotten the version of your Ubuntu OS then follow this tutorial which explains how to find the Ubuntu version. Open the Terminal (keyboard shortcut: Ctrl+Alt+T) In the terminal type following command: Your version will be shown on
To find version of Ubuntu/Debian, you can run Example This way show exact point release, for example this is Debian 8.8. You can use lsb_release command to find more details, lets first install lsb_release if not already installed. Now run