Casting objects in Unity using a local class of an object

I know it sounds weird, but I have this situation going on. psuedo/simplified code, in essence, I'm trying to be able to access data/variables from "foo"'s "inner foo" class from "bar."

 public class foo
 {
 ArrayList pass;
 public class innerFoo
 {
 //stuff in here
 }
 void start()
 {
 pass = new ArrayList();
 pass.Add(new innerfoo());
 }
 
 }
 
 public class bar
 {
 public gameObjectWithFoo O;
 void start()
 {
 ArrayList LIST = new ArrayList();
 LIST.add(O.pass[0]);
 //
 //Here is where I'm stuck, How would I cast LIST[0] as the innerfoo type, the ArrayList<ObjectType> syntax isn't working either...
 //
 
 }
 }