CoinGame.cs

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

public class CoinGame : MonoBehaviour
{
    [SerializeField]
    private GameObject coin;
    private const int MAX_COIN = 10;

    // Start is called before the firsst frame update
    void Start()
    {
        System.Random random = new System.Random();

        // Create Coin
        for(int i = 0; i < MAX_COIN; i++)
        {
            var go = Instantiate(
                coin, 
                new Vector3(
                    transform.position.x,
                    transform.position.y+3,
                    transform.position.z
                ),
                transform.rotation
            );

            // random
            int positionX = random.Next(-50, 50);
            int positionZ = random.Next(-50, 50);
            go.GetComponent<Transform>().position = new Vector3(
                positionX,
                go.GetComponent<Transform>().position.y,
                positionZ
            );
        }
    }

}