Thank for hint, l think I forgot to mention I am not well versed with dreamhost and we are org of 3 to 4 people who support cause to help people. Most of us are very non tech.
Also how would one migrate http://xyz.org/abc to http://abc.xyz.org
please note the exiting site is http://xyz.org/abc (which is actually) a subsite like many other...
As far as http://pqr.xyz.org (note PQR instead) they are new method of creating subdomain within parent site.
I would request you to please give me more details and example so that I can achieve the above.