How change object type, when child inherit from same parent but have difrrent method and props

In college I got task to do. I have simple program like below. I have one parent class who represent person, and few child which inherit from it and represent role(Archer, Knight, Wizzard). I must implemented funcionality to easy switching object type, from Archer to Knight and so on. At first I thought about creating a large interface with all the unique methods, but it breaks the SOLID rule, but I can't break this rule. Could someone help figure it out?

This is how look code:

public abstract class Person
    {
        public String Name;
        
        public char Age;
        
        void describe()
        {
            //some code
        }
    }

Role class:

public class Archer : Person
    {
        public int agility;

        public void describe()
        {
            //some code
        }

        public void fightUsingBow()
        {
            //some code
        }
    }

Next role:

class Wizzard : Person
    {
        public int mana;

        public void describe()
        {
            //some code
        }
        
        public void castASpell()
        {
            //some code
        }
    }

You can't just "switch" an archer to a knight. An archer is not a knight. You could create a new knight using the same base properties of the archer, but there's no built-in way to do that. One way is to use a "copy constructor" for a person - something like:

public Person(Person basePerson)
{
    this.Name = basePerson.Name;
    this.Age = basePerson.Age
}

then add a constructor to Knight that calls the copy constructor:

public Knight(Person basePerson) : base(basePerson) {}