The Garmin Express app should be able to check if you are able to upgrade to the latest. With the recent changes to support for Operating Systems like Mac OSX 10.6 and Windows XP you might not be able to upgrade to the latest if you have these operating systems. If you are running a compatible operating system you can try downloading the latest version here. Once the file is download you should be able to open the installer and follow the process.
The version of Garmin Express you are looking for has not be released to all Customers. I will provide you with a special link to upgrade to it so you have it though. Garmin Express 3.1.9 You should be able to get the latest version here. Garmin routinely places a small amount to receive the latest version before doing a full launch of the software.