I'm having difficulty getting tones I downloaded to show up on my iPhone through iTunes

I downloaded some simple tones off the internet as mp3s to use on my iPhone. I converted them to both m4r and AAC, and all 3 formats will not show up when I transfer them through the File Sharing option on iTunes when you have your iPhone plugged in. I've done this before with other tones with the same converter software with no issues, and the tones play if I open them in iTunes, so I'm confused why I can't get them to work. Does anyone have any suggestions? Thanks for any help.