Auto Category Placement?

Hello,

I have searched but I cannot find a plug-in that will suit my needs… I am hoping that someone here will be able to point me in the right direction.

I have a ton of posts on my site and I would like to re-categorize these posts. I have been going through my site manually to find posts with specific key words that I have searched for, then I add the results individually into a specific category that matches the keyword that I searched for.

Here is my question… Is there a plug-in available that will allow me to search my posts then be able to add all of the posts that match the search to a specific category, avoiding the need to search –> select specific post –> edit–> add to category –> save –> repeat?

Any help would be wonderful!