Setting in iTunes for all songs to be done in mp3 format. Also with ones have done ACC conversion why does it do copy of it and how do I know which one I can use on my mp3 player?

Hi ColColG'day,

If you import songs from CDs into iTunes, you can set it to use mp3 as the encoding format with iTunes' preferences. This article describes how - iTunes 12 for Windows: Choose import settings.

Songs that are already in iTunes as AAC may be converted to mp3 using the steps in this article - iTunes: How to convert a song to a different file format.

For the settings needed to use a song in your mp3 player, consult the manufacturer of the player.

Thanks for using Apple Support Communities.

Sincerely.