How do I know if my music is in my icloud?

How do I know if my music is in my iCloud?

I recently got a new phone and i received a SIM card to put in it but I want all my songs from my old phone to be on the new phone. I am not sure if my music is in the iCloud. In my iTunes library I see half the songs with the little iCloud symbol but I don't know what clicking that does. If anyone can help me that would be great! Thanks!