Where Can I find specific sites powered by Wordpress ?
It's not hard to find websites powered by Wordpress. In fact, years ago all sites received this branding. Things have changed though and website owners have the ability to remove the branding. However, you can browse a specific search engine to find out for sure.
Using the is it Wordpress search engine for now is one of the best solutions, if not "the best" solution for this area of curiosity. You can find it here: Is It Wordpress.