The version of the gallery you are running pre-dates it becoming an official XenForo product. When it became a XenForo product, it was renamed to XenForo Media Gallery and the version number was reset to version 1.0.0. The current version is 1.1.2.
Xen Media Gallery licenses were transferred automatically to the XenForo customer area. Therefore you would need to upgrade by downloading the appropriate Media Gallery version from your customer area. I would recommend using the latest version.