Converted files in iTunes, now I have duplicates?

So I picked up an iRiver clix and tried putting music on it drag and drop style. When I did, I discovered that all my music was in .m4a style and wouldnt work on the player. I then converted all my music to .mp3 style so it would work. Low and behold, I now have duplicates of all my songs in both formats. Granted the .mp3 songs work on the player now, its rather annoying having doubles of everything in my playlist on itunes.

I did a search for all .m4a extensions and sent them to the trash and emptied the trash. Unfortunately, they are all still in my playlist but not in my folders.

How do I update my itunes to only show the new .mp3 formatted songs?

You can add "kind" to the bar at the top where you choose artist/ title/ name/ time, etc... If you add kind, you are able to sort by the type of file it is. You can easily delete all the extra songs in the playlist that were previously deleted from the library.
I would think this would have happened automatically but I am not all that iTunes knowledgable.

Thanks, that adding the "kind" label helped sort it out to be able to delete them all in my playlist.