I made a post but the post was deleted. I do not know why. How do I send a message to a moderator to find out?
Asking here on meta is an excellent way to get all the moderators to have a look. Everyone past a set level of reputation gets to cast votes to delete posts or close them so there are many moderators here.
In your case you posted an answer here that didn’t meet the quality standard for a direct answer to the question: https://apple.stackexchange.com/a/465557/5472
All first posts on a site by a user enter a review queue that trusted members of the community can view to ensure everyone has a good experience. Two users evaluated your “answer” as “not an answer” and after those comments a third user flagged it as not an answer. I agreed and deleted the post about 6 hours after it was initially posted and reviewed.
You now have answered a second time, and that answer doesn’t look to have enough detail to be kept up. I’d rather it not get down votes while you have time to edit it into shape.
I would recommend you edit your original post and then flag it for one of the elected moderators to review once you have all your edits done. This can happen in a day, a week or a month. Take your time.