Programaticly Spawn Powerups?

How can I programaticly spawn powerups? I need an example in c# of how to do this. My complete code is as follows:

 using UnityEngine;
 using System.Collections;
 using System.Timers;
 
 public class Random_Powerup_Generation : MonoBehaviour 
 {
     private static Timer PowerupTimer;
     private int newPower;
 
     // Use this for initialization
     void Start () 
     {
         //randomize timer to int between 15000 and 45000
         double powerupInterval = Random.Range(15000,45000);
         //create timer
         PowerupTimer = new Timer(powerupInterval);
         //create the event for the timer
         PowerupTimer.Elapsed += new ElapsedEventHandler (CreateNewPowerup);
         //start timer
         PowerupTimer.Start();
         //Make sure it resets
         PowerupTimer.AutoReset = true;
     }
 
     // Update is called once per frame
     void Update ()
     {
         //random powerup
         newPower = 0; //Random.Range(0,2);
     }
     
     void CreateNewPowerup(object source, ElapsedEventArgs e)
     {
         //create new powerup
         
         switch (newPower)
         {
             case 0:
             break;
             case 1:
             break;
             case 2:
             break;
         }
     }
 }

My powerups are in prefabs, and an example of a name is pre_HealthPowerup.