I want new music on my iphone?

But since I erased the other iTunes and downloaded anther one when I plugged in my device it doesn't show so I can't put music on my iPhone please help

If you bought your songs in iTunes, just open the iTunes app on your iPhone, then push Purchased. It should bring up the songs you bought, and you can download them for free.

"I erased the other iTunes "

You mean you erased the music or you uninstalled the program?

"hen I plugged in my device it doesn't show"

what doesn't show? The device or the music that's on it?