Modify .htaccess

[teyes]

I am running a invisionboard. Personally, I feel that google has the tendency to index html pages at a higher rank compare to dynamic pages. I am on a Apache server with mod_rewrite enabled. I am running invisionboard V1.2
How do I change
http://www.lioncity.net/buddhism/index. ... wtopic=361
to
http://www.lioncity.net/buddhism/index. ... c/361.html

How do I modify my .htaccess?
Thanks in advance.