Should I message him? What should I say?

I’ve known this guy for almost 10 years but we haven’t talked in a few years. I had a crush on him a long time ago because he’s a really good guy, but we were just friends. I’m in a position where I have literally no friends or anyone, do you think it would be weird if I reached out to him? And if so, what should I say? I just really need a friend and he still likes my stuff on Facebook occasionally so not sure if it would be weird.

(I’m autistic so knowing if this is socially appropriate and what I should say is difficult for me)