AI in unity, need help

I need some help with my AI I was working on, my code below

using UnityEngine;
using System.Collections;

public class NewAITest : MonoBehaviour
{
	public float motionSpeed = 1f;
	
	void Update()
	{
		// Rays
		Vector3 upRay = transform.TransformDirection(Vector3.forward);
		Vector3 downRay = transform.TransformDirection(Vector3.down);
		
		// Up and down motion
		if(Physics.Raycast(transform.position,upRay,2))
		{
			transform.Translate(Vector3.back *  * Time.deltaTime);
		}
		
		else if(Physics.Raycast(transform.position,downRay,2))
		{
			transform.Translate(Vector3.forward * 1 * Time.deltaTime);
		}
	}
}

You mean -Vector3.forward?

forward, up, right etc are all verbal ways of expressing a numerical vector.

0,0,1 = forward (z axis)
0,0,-1 = backward

0,1,0 = up (y axis)
0,-1,0 = down