If you used the same gmail address and password ***** the new phone it should restore whatever you had on the old phone. This is dependent on how well you had it backed up though. They usually default to backing it up but if you were having sync errors and didnt correct it or told it not to back up than it wont be there to restore of course.
that is for an android for an iphone the same will be true but it would be backing up to icloud or itunes and you would have to use your apple id on the new phone.
If the pandora is still not there you can go to the app store either google or apple and install it again.
you can install it on a droid from this link
one note. If you were previously using an iphone and got a new droid or vice versa your restore options are a lot more limited and you would have to reinstall any apps manually including pandora.