Is there an app which allows the transfer and then playing of music from a nas?

Hello, i just got my first iphone having been a mac user for years. I also have a nas with tons of music on which i use for playback on a sonos. I used to be able to download some music from it onto my android phone to play int he car, but there doesn't seem to be an obvious way to do this on the iphone?

Any suggestions?