c# script

private Save sv = new Save();
//...
private void Awake()
    {
        if (PlayerPrefs.HasKey("SV"))
        {
            Debug.Log("AWAKE");
            sv = JsonUtility.FromJson<Save>(PlayerPrefs.GetString("SV"));
            copper_coins = sv.copper_coins;
            silver_coins = sv.silver_coins;
            gold_coins = sv.gold_coins;
        }
    }
    private void OnApplicationQuit()
    {
        Debug.Log("OAQ");
        sv.copper_coins = copper_coins;
        sv.silver_coins = silver_coins;
        sv.gold_coins = gold_coins;
        PlayerPrefs.SetString("SV", JsonUtility.ToJson(sv));

    }
//...
[Serializable]
public class Save
{
    public int copper_coins;
    public int silver_coins;
    public int gold_coins;
}