The permalink structure in your WordPress blog determines what type of extension your posts have. If you have ever wanted to change from one permalink structure to another but didn’t because you would lose a lot of traffic then this is the plugin for you.
If you just migrated your WordPress blog from one permalink structure to another, and you don’t want to lose the traffic that accesses your blog through the old permalinks, this is for you.
Right before the old permalink generates a 404, this simple plugin grabs the slug from the end of the request and checks if there’s a post with this slug living somewhere else on your blog. If so, it will generate a “301 Moved Permanently” error, and forward your user to the new location of your post. It’s simple, but effective.
I love plugins like this, they take a problematic situation and resolve it with the simple upload and activation of a plugin.
Download Link : Permalinks Moved Permanently Plugin