I can’t transfer music onto my San disk from Itunes

So I have an ITunes subscription, and I’m trying to transfer what’s in my playlist to my sandisk, but it won’t let me. There was one song that I bought separately for 1 dollar and it allowed that song to be transferred but not any of the other songs, and I’m not about to pay for ALL of my songs individually that I have on iTunes. Is there another way? I tried using drag and drop method and copy and paste but still didn’t work. It just puts a little error stop sign and doesn’t transfer the song.