Mahalo nui, Kim . . . .
For the uninitiated, and those without access to Plone core on github, you can find this folder in your Plone 4.x filesystem under buildout-cache/eggs/Products.ATContentTypes-etc. It is the same in Plone 5 because P5 continues support for Archetypes. I haven't tried to find the Dexterity-based version.
For coders these are trivial questions - this reference is for those without that expertise.