How to download files from MediaFire directly on iPad?
It is not possible to download an mp3 file from a site like MediaFire and place it directly in the Music app on your iPad. 

There are some app where you can download a file to listen it later, sorry i don't know the name of one of those apps.

The options you have are


to download it on a computer and sync your iPad
to jailbreak your device and use iFile to access the mp3 file