Need help with iPod

Before I bought an iPod Nano I had created lots of playlists in Windows Media Player. Now that I have an iPod I want to put these playlists on my iPod. All the songs are in .mp3 format. I looked on the Internet and followed instructions for converting these .wpl files into .m3u format which is the format that iTunes uses. I’ve tried importing these .m3u files into iTunes with no luck. Within iTunes I click on File, Library, Import Playlist, then choose the .m3u file to be imported. It creates a folder in the iTunes Playlists with the name of the playlist but does not bring in any of the songs from the playlist. What am I doing wrong? Hopefully, somebody on the forum can help me so I don't have to recreate all of my old playlists.