How to access all my old tracks on Apple Music without paying again?

Over the years I have bought individual tracks and albums from iTunes. These are stored on my phone. I can see them. But I can’t listen to certain tracks when I try I’m direct to buy subscription from Apple Music. Why should I have to pay again for Music, I’ve already paid for. Is there any way around this? Thank you?

[Re-Titled by Moderator]

Original Title: I Apple Music subscription