As @C_Sharp_Gaming said, you’re trying to access the parent.
A “parent” in unity is the game object that is above in the hierarchie.
In your case you could have the Destroyer script on your “car” or “bike” GameObjects so when you write this:
if (Object == null)
Object = transform.parent.gameObject;
Your saying that you will destroy the “Vehicle” GameObject but I guess you don’t have any parent like in the image so you don’t have go with a variable, you can just Destroy(gameObject) since the “gameObject” here represent the one where your script is attached to.