collectable currency doesn't transfer between different scenes

ok so basically I have two scripts to do with currency in my game at the moment, one which adds money when I collide with an object (like a coin) and deletes it. And one which shows how much money I have in a UI Element and the problem I have is that the money doesn't transfer between different scenes and I'm really struggling to find a way to fix this fairly easily

Currency Script:

using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.UI;

public class Currency : MonoBehaviour {

 public int gold;
 GameObject currencyUI;

 void Start()
 {
     currencyUI = GameObject.Find("Currency");
 }
 void Update()
 {
     currencyUI.GetComponent<Text>().text = gold.ToString();
     if (gold < 0)
     {
         gold = 0;
     }
 }

}

And the pick up money script:

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class PickUpMoney : MonoBehaviour {

 Currency script;

 public int addAmount;

 void Start()
 {
     script = GameObject.FindWithTag("GameController").GetComponent<Currency>();
 }

 void OnTriggerEnter(Collider obj)
 {
     if (obj.gameObject.tag == "Player")
     {
         script.gold += addAmount;
         Destroy(gameObject);
     }
 }

}

i'd be very happy if someone could explain what I could do to be able to transfer the amount of money I have in one scene into another scene and back an forth etc.!! thank you