Unlike Windows operating system which clearly shows which service pack you have installed, it can be a bit tricker to keep tabs on which version of Exchange you are running.
For Exchange 2007, 2010, and 2013 you can use the Exchange Management Shell, with the following command:
Get-ExchangeServer | fl name, edition, admindisplayversion
Or you can use the Exchange Management Console, and click the Help menu, About Exchange Server 2010.
Now you know the version number you are running, check the post below to see which service pack/update rollup the version number refers to.