Get-ExchangeServer | fl name,edition,admindisplayversion
Get your server version,build version
http://justaucguy.wordpress.com/2013/04/09/exchange-version-check-2013-cumulative-updates/
Verify the numbers you get from this page. Here is the chart that is currently on the page now:
Your Exchange Server version can also be viewed in the EAC:
dowunload Exchange server2013 cumulative update 1(kb2816900)
http://www.microsoft.com/en-us/download/details.aspx?id=38176