change name of url

I have the following sub-domains:
ceconn.com/canwetalk;
ceconn.com/saycheese;
ceconn.com/whatsmellssogood

I would like to change the names of sub-domains to read:
ceconn.com/can-we-talk;
ceconn.com/say-cheese;
ceconn.com/what-smells-so-good

My reason? I’ve been told that for better placement, my keywords should be in the url and that it should have the dash or underscore so that the search engines can find them.

I’d like to do this without screwing everything up. Can you guide me, please?