The easiest ways to find your version:
Login to admin and view the version in the footer
..or
Enter the following information in your browser.
http://[yoursite]/downloader
Here is the the official Magento article for more information
http://www.magentocommerce.com/wiki/groups/227/check_magento_version
Article ID: 64, Created: 12/3/2013 at 9:35 AM, Modified: 10/30/2014 at 8:05 PM