htaccess and rewrites.

I have a situation where ive combined 3 wordpress sites into one site.
The new and aggreed upon post type is the “post name” method or > http://nypress.com/sample-post/ now the old sites all used different versions, the domains all point to the new domain, but in instances where i have old links out there like > http://ourtownny.com/2011/03/30/the-comeback/ dont work. I need to rewrite them as
http://nypress.com/the-comeback/ anyone have a pointer or idea what i should be doing? My current htaccess looks like >

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

thanks in advance.

j