How do I reward the players with coins after they watch a Admob rewarded video?

Ok, I am using the same script that everyone is using, by that I mean the script given by google.
I already created an AdMob rewardedVideo Unit and the type is “coins” and the amount is 300

I have not idea how to reference this 300 amount to my coins
amount in the game. I am confused and do not know where to go next.

void Start(){
 // Called when the user should be rewarded for watching a video.
        rewardBasedVideo.OnAdRewarded += HandleRewardBasedVideoRewarded;
}

public void HandleRewardBasedVideoRewarded(object sender, Reward args)
    {
        string type = args.Type;
        double amount = args.Amount;
        print("here");
        MonoBehaviour.print("HandleRewardBasedVideoRewarded event received for " + amount.ToString() + " " + type);
    }

        public void ShowRewardedVids()
    {
        if (rewardBasedVideo.IsLoaded())
        {
            rewardBasedVideo.Show();
        }
    }

if this help, I usually add coins and save them like that.

 ScoreManager.GetInstance().savecoin += 300;
                ScoreManager.GetInstance().Save();

Ok maybe I have missed something in my understanding of your question, but it should only be a matter of adapting the HandleRewardBasedVideoRewarded function like so :

public void HandleRewardBasedVideoRewarded(object sender, Reward args)
 {
 
      string type = args.Type; //Reward type ("coins" if everything goes fine)
      double amount = args.Amount; //Reward amount (300 or else)
 
      if(type == "coins")
      {
           ScoreManager.GetInstance().savecoin += (int)amount;
           ScoreManager.GetInstance().Save();
      }
 
 }