You may potentially convert an SP world to a mac server, but you can only do so in certain circumstances. Wingy, for his part has probably spent countless hours creating a system to improve the experience of those who use his hosting service for servers, but these systems are incompatible with the world conversion.
To my knowledge, @Joe and @222oreo333 also host mac worlds but I don’t know if they’re still accepting requests.
As of yet, there’s no system to convert cloud worlds to mac or single-player versions, though I’d imagine you could potentially turn a mac world into a cloud world using a process similar to the Blockserver>Cloud conversion.
Mind you, I wasn’t here 4-6 years ago so I don’t if Blockserver was run on a mac or not. I’m also by no means an expert on the workings of computers, so you should likely dutifully ignore this post and wait for someone else to answer.