From then till the end of the year, users of Google Play Music will be able to transfer their music libraries to YouTube Music, the app Google is replacing it with. If people don’t move their libraries during 2020, they will become unavailable into 2021.
Transferring your library over to Play Music will move and restore any music purchases you’ve made as well as your playlists. If you want to physically download your purchases you can do so using Google’s Takeout tool.
In addition to this, Google has announced that music will no longer be available to download at all from a Google service with the shuttering of Play Music. This change will happen in late August, and means there will no longer be a way to purchase or download music from Google.
If you want to move purchased music to YouTube Music, you’ll have to purchase it from another source and transfer it across.