Purchased songs from iphone to computer

Hello experts,

I was asked to synchronize my father's iPhone to his laptop but I am having some issues on it. When he first purchased his iPhone, I synced it on my own laptop. But that was few months ago and now the iPhone is out of sync. He purchased some music and applications. But the default library where I synchronized his iPhone does not exist after configuring my new laptop.

My question is, how can I sync his device on his own laptop without losing all the music and apps that he purchased? As of now, I copied all the contents of his iPhone to his laptop with all his old data. Is it okay to just copied the library from his iPhone to iTunes? And get his purchased files from the iTunes Store to iTunes in his laptop.