Roll a ball movement isnt working (Script)

im getting errors in my script and do not know how to resolve them

using UnityEngine; The type or namespace name ‘UnityEngine’ could not be found (are you missing a using directive or an assembly reference?)
using System.Collections;

public class PlayerController : MonoBehaviour The type or namespace name ‘MonoBehaviour’ could not be found (are you missing a using directive or an assembly reference?)

public float speed;

private Rigidbody rb;The type or namespace name 'Rigidbody' could not be found (are you missing a using directive or an assembly reference?) 

void Start ()
{
	rb = GetComponent<Rigidbody>();
}

void FixedUpdate ()
{
	float moveHorizontal = Input.GetAxis ("Horizontal");
	float moveVertical = Input.GetAxis ("Vertical");

	Vector3 movement = new Vector3 (moveHorizontal, 0.0f, moveVertical);

	rb.AddForce (movement * speed);
}

}

It turned out i couldn’t have my project destination on a flash drive since unity was installed to my c drive which sucks because i am using a desktop and need to be able to use a flash drive so i can transfer my work to school so i’m not sure how to resolve that but now my program is working.