Q. My instructor says I have to use a .org site. Is there a way to search just .org?

Yes, there is. Google can help you with with that:

1. Go to Google advanced search.
2. Type in your search terms as normal.
3. Scroll down the page until you see the Search within a site or domain: box and type in .org
4. Now all your results will be from .org sites.

You can use the same technique with .com, .edu, .gov and so on. You can also use this feature to restrict your search to a specific site this way like google.com. Find out more about Google from out Google guide or the Google Books, Magazines & News Archives guide.