You're fine, assuming you have a computer. I don't think you can download directly to your iPad.
You have a couple of options.
1) Buy the mp3s and download to your computer. From your computer, you can drag them to your iPad.
2)
(This will only work if you will listen to the music where you have WiFi, or you have a good data plan. This will eat up data). Buy the mp3s, and keep them on the
Amazon cloud (a server offsite). Then go to the Apple apps store and get the Amazon Cloud Player. You can assess all of your Amazon mp3s that way.
Probably would be best to buy the mp3s, download them to your computer, then connect the iPad and drag from the computer to the iPad. Me...I have an iPhone, and don't have too much more space, so I keep my Amazon mp3s on the cloud and listen at home where I have wifi.
Anyway, you'll be fine. Have fun.