Reaching out to old friends?

I lost touch with my friends from high school once we left for college (more like the 3 of them all stayed in touch but forgot about me). I’ve really been wanting to reach out to them and get in touch again, but don’t know how, especially because things ended on kind of a sour note. People tell me to move on from them, but I haven’t made many friends in college and am graduated from college now. Despite not being friends with them for 3 years, I still really miss them. I was friends with them since middle school, and one of them since 1st grade... how do you reconnect with old friends? Especially not knowing if they even want to talk to me or not... I’ve struggled with making new friends and miss my old friends. A simple “hey”? Ask if they want to talk again?