How do I know which version I have? I know it is 11 pro but not know which service release?
In the top menu, choose "Help" then "About Poser." You'll see the release number at the bottom left of the graphic, under your licensee name.
However, for Poser 11 Pro, all you have to do is go to the Preferences, General Preferences, Miscl tab and click on the "Now" Check for Updates button. It is set to check for updates on startup by default, but if it's not checking, just do it manually. If there is an update you need, it will prompt you to run the update utility.