location of DTSX package
On your server, there is a file named MsDtsSrvr.ini.xml which is located at C:\Program Files\Microsoft SQL Server\120\DTS\Binn (for sql server 2014). When I examined this file it stated "..\packages" for the location, so I went to the DTS folder then into the packages folder and the files were there.

Depending on your version, architecture, and installation path) of SQL Server, you might find these files at 


C:\Program Files\Microsoft SQL Server\90\DTS\Binn\MsDtsSrvr.ini.xml (2005)
C:\Program Files\Microsoft SQL Server\100\DTS\Binn\MsDtsSrvr.ini.xml (2008/2008R2)
C:\Program Files\Microsoft SQL Server\110\DTS\Binn\MsDtsSrvr.ini.xml (2012)
C:\Program Files\Microsoft SQL Server\120\DTS\Binn\MsDtsSrvr.ini.xml (2014)
C:\Program Files\Microsoft SQL Server\130\DTS\Binn\MsDtsSrvr.ini.xml (2016)