iTunes 
Check for iTunes Store purchases
When you open iTunes, it checks for iTunes Store purchases that haven’t been downloaded to your computer.
You can also check for purchases that haven’t been downloaded. You might want to do this, for example, if a download was interrupted.
Make sure all your purchases have been downloaded
Make sure you’re connected to the Internet.
In iTunes, choose Store > Check for Available Downloads.
Enter your Apple ID and password (if requested), and click Check.
Purchases not yet on your computer are downloaded.
Items you purchase from the iTunes Store are added to the Purchased playlist in iTunes. However, because you can add items to or remove items from this list, it might not be accurate. To see all your purchases, click iTunes Store, click Account, log in, click Purchase History, and click See All.
If you delete the Purchased playlist, iTunes creates a new one when you buy an item from the iTunes Store.