Trying to get my pong AI to work

So I am a total beginner in coding. I am trying to get my Pong AI to work and I am using the Vector3.MoveTowards.
I have searched for people with similar problems but often I don’t understand the answers given. Or the answer is given in Java and I don’t know how to convert it to c#.

using UnityEngine;
using System.Collections;

public class EnemyAI : MonoBehaviour {

	Transform Ball;
	public float speed = 10;
	float movey;

	void Start()
		Ball = GameObject.FindGameObjectWithTag ("Ball").transform;
	// Update is called once per frame
	void Update () 
		Vector3 giPos = Ball.transform.position;
		giPos.y = movey;
		Ball.transform.position = giPos;
		float step = speed * Time.deltaTime;
		transform.position = Vector3.MoveTowards (transform.position, movey, step);

Anyway, this is my code so far. It returns an compiler error in unity saying:
CS1502: The best overloaded method match for UnityEngine.Vector3.MoveTowards(UnityEngine.Vector3, UnityEngine.Vector3, float)' has some invalid arguments And also: CS1503: Argument #2’ cannot convert float' expression to type UnityEngine.Vector3’

I understand that the “movey” thing is what is causing the error but I am at a complete loss on how to fix it. I feel stupid for asking but I’m banging my head against the wall. Feels like I have tried everything.

the problem is that movey is a float and Vector3.MoveTowards requires a Vector3 instead of a float where movey is. So an easy fix would be to add:

Vector3 newPos = new Vector3(someXValue, movey, someZValue);

and then replace movey in the Vector3.Movetowards with newPos. Also, you might want to change:

giPos.y = movey


movey = giPos.y