Can anyone explain this error and what I need to do to get around it? I'm so lost. I'll put code in comments.

public class Units: MonoBehaviour  
{  
public int unitHealth;  
public int unitDamage;  
public int unitMovement;  
public (int, int, int) Tank()  
{  
Units tank = new Units();  
tank.unitHealth = 100;  
tank.unitDamage = 20;  
tank.unitMovement = 1;  
return(tank.unitHealth, tank.unitDamage, tank.unitMovement);  
}  
public (int, int, int) Warrior()  
{  
Units warrior = new Units();  
warrior.unitHealth = 60;  
warrior.unitDamage = 40;  
warrior.unitMovement = 2;  
return(warrior.unitHealth, warrior.unitDamage, warrior.unitMovement);  
}  
public (int, int, int) Archer()  
{  
Units archer = new Units();  
archer.unitHealth = 20;  
archer.unitDamage = 50;  
archer.unitMovement = 1;  
return(archer.unitHealth, archer.unitDamage, archer.unitMovement);  
}  
public (int, int, int) Mage()  
{  
Units mage = new Units();  
mage.unitHealth = 10;  
mage.unitDamage = 60;  
mage.unitMovement = 1;  
return(mage.unitHealth, mage.unitDamage, mage.unitMovement);  
}  
public (int, int, int) Rouge()  
{  
Units rouge = new Units();  
rouge.unitHealth = 10;  
rouge.unitDamage = 20;  
rouge.unitMovement = 5;  
return(rouge.unitHealth, rouge.unitDamage, rouge.unitMovement);  
}  
}  
}
/r/Unity3D Thread Parent Link - i.redd.it