Upgrading from 3.x, want to change URL structure
 

I've been running a forum for some time now and I'm looking to upgrade to v4.

One of the changes that I want to implement is changing the URL structure.

Today, my forum has the following structure: domain.com/forum

I want domain.com to load the forum directory directly.

What is the best way to do this without losing traffic from search engines? I want to have as few broken URLs as possible. Is there some htaccess that I can use for this? I would like to redirect the traffic coming in from search engines to a specific topic to its new URL, without the /forum/.

Thanks!