In German, we call this Deppenapostroph since many use this ‘ for building the plural.
Guess in English it’s getting incorrect more and more as well… so why don’t you jsut rename the folder to its correct form MP3s? 😆 (or is there any special reason you can’t rename it currently? If it’s just about NTFS, some kind of live CD with NTFS writing enabled (or even a BartPE CD) may suffice if its just that you don’t have any Windows installed currently).
(and yes, I’m allowed to make fun of it, I’m not really better since I made the same mistake when creating the smart playlist wizard 😉 )