To find out what version of Zen Cart or PHP or MySQL you are currently using, you can simply go to Admin->Tools->Server Info
On that screen you will see a lot of detail about your server configuration. Your Zen Cart version will be shown, as well as your server's PHP version, MySQL version, various database statistics, some basic PHP settings, and more.
You can also see your database-upgrade history.
Your server's PHP configuration details will also be shown.