MP3's from iPad to iMac

[FevLad]

Hi, I searched this forum but can't find a solution to my problem.

I have stacks of MP3's on my iPad purchased from Amazon, but I can't get them on to my newly purchased iMac via iTunes. Is there any other way to do this?

iTunes will transfer the tracks I have bought from Apple .. but not mp3's I have bought from Amazon. What's the deal here?
I tried right clicking on the ipad in iTunes and transferring purchases but it just migrated apps and books ... but not music??

Hope someone has a solution.

FevLad