Following Neil's post ... the DVD will arrive as 10.6.3. You should then update it further, via the combo update, to 10.6.8 which will bring you the App Store.
I know you haven't asked but If you hope to go further, read up on the OSX system requirements. Some early intel machines may not work with Mountain Lion, for example.
Minimum specs for Mountain Lion. http://www.apple.com/osx/specs/