Random generation of Asteroids

Hello, i want to generate an Astroid field. I want to place them at random places around a coordinate with a max and min amount of asteroids or something like that. I found the instantiate command but im not sure how i would make the center var and the random range from that. And how do i make it so the "SpawnLoop" only runs as long as i want asteroids to be generated.I have 5 diffrent Asteroid Prefabs that i want to randomly choose from. And is there a way to only spawn in places that are far enough away from other asteroids? I know these are alot of questions but it would be very helpful if someone can explain and help me with those. Thanks in advance.