How to make friends outside work/within any environment/setting?

I’m an adult who has trouble making friends. Not that I have no friends I do have some pretty loyal friends but the thing is I want to be more social and outgoing. I have always have trouble being social because I was diagnosed with autism in my teens. While I was at ucf I’ve taken a group therapy session meant to help individuals like me get more social and make friends but that really didn’t work for me. I’m just looking for some generally advice, how can I make new friends with my co-workers at work? At what situations should I talk with them? How do I get outside my shell and find friends outside of work? Is it possible to make friends anywhere at any situation? Like, even if you are stuck in a line at Walmart and you talk to the person behind you? At what situations should you try to butt in a group conversation to try to make friends with a group when its appropriate? What do you talk about if you do talk to strangers? How to sense they don’t want to talk to you and how do you keep conversations going for strangers? Sorry if this seems like a info doubt but I really want to be in a position in which no matter which place I’m in, or what the situation is, if there is people around me, I walk to socialize with them and turn them into friends. Lastly, if the person seems to be friendly with you enough, when it is right time to ask for their phone number to continue to socialize as friends?