music

I Recently got a Samsung S8 after years of having the iphone,so im after a program or whatever there called so i can put all music onto and use it to transfer music to the S8,ie something like itunes where i can pick somngs,make playlists etc please.

Recently bought a new kenwood headunit with all the usb/Bluetooth etc on it,but i don't want to keep using my phone for the music so today I went and bought a FlashDrive.But its not working out how I wanted it to be,ive found out how to put music from my iTunes to the flashdrive but I cant do it...