6
It's named something like xoops-2.0.5.2/html/templates_c in the XOOPS distribution. The files in the html subdirectory are copied to whatever directory you've chosen as your XOOPS web root, which need not be "html".
(The above applies to XOOPS 2. I haven't used XOOPS 1, so I don't know if they're the same in this respect.)