rar: How to figure out the entry for sources.list

[Harry Putnam <reader@newsguy.com>]

How does on go about figuring out the exact entry for
/etc/apt/sources.list in order to download packages
like rar?

I googled and found such an entry for lenny:
  deb ftp://ftp.us.debian.org/debian/ lenny non-free
  deb http://security.debian.org/ lenny/updates non-free
  deb http://volatile.debian.org/debian-volatile lenny/volatile non-free

Is it as simple as just inserting wheezy for lenny?

And if I didn't find that google hit.  Is there some way to figure
that out from the search at:

http://packages.debian.org/search?searchon=names&suite=all&section=all&keywords=rar