How to change a moving box's direction once it hits a point?

In the attached file I have a picture showing a red box and a blue box. The red box will be moving down until it reaches the the blue box's horizontal coordinates. The question I have is: how do I change the direction it is going to be going once it hits that position? I have tried:

//this script is on the red box

function Update () {

 transform.Translate(0, 0, -5 * Time.deltaTime);

 var myPosition = transform.position;
 
 if(myPosition == Vector3(10, 3, 0)) {
 
 transform.Translate(-5 * Time.deltaTime, 0, 0);
 
 }

}

This may be obvious to you, but I am very fresh off of the boat on scripting so any help would be kindly taken.

Thank you.