Two points - you need the -R *before* the 664 and even if you're in the
folder you want to change, you need to tell it what to chmod, so you
need to cd to the directory and 'chmod -R 664 .' or 'chmod 664 *' should
work as well if there are no sub-folders - you don't need the 'sudo' if
the files are all owned by the logged in user, presumably yourself.

Ok. I screwed up in what I was asking.

I need to change the group to www-data from abc.

How do I also change the group?

I reading this page on File Permissions:

suds chown www-data abc

But Im not getting - does this do all the files in a folder?
Its not recursive?

You need the -R (for recursive) option: chown -R www-date wadesmart
chown, chmod, chgrp all work the same