You would probably be best off having a script that tracks where the player should respawn. It should hold a reference to the current respawn transform, and that reference should be updated as the player walks into each respawn trigger.

eg. RespawnTracker.cs

Transform currentRespawnPos;

public void SetNewRespawn(Transform newRespawn)
{
    currentRespawnPos = newRespawn;
}

public Transform GetRespawnPosition()
{
    return currentRespawnPos;
}

Then have this script on each of the respawn triggers

RespawnTrigger.cs

// Hold  reference to the RespawnTracker
// Either drag and drop the reference in editor or write some code to set it
RespawnTracker respawnTracker;

void OnTriggerEnter(Collider other)
{
    // You will need to fill this out with a proper test suitable to your project
    // Read as psuedo code
    if(other == player)
    {
        respawnTracker.SetNewRespawn(transform);
    }
}

From there, the player just needs to call the respawn tracker to get the position of the last checkpoint.

Just as a quick note, using GameObject.Find() during the game's runtime can be very slow, especially as you get more and more objects in your scene. It is better to find anything you can at the start of loading a level, or store references by dragging them onto scripts during editing where possible.

create a script for your player and write a code like this

function OnTriggerEnter (other : Collider)
{
   if (other.name == "spawnpoint")
   {
      this.spawnPosition = other.transform.position;
   }
}

just set the name of all spawn point gameObjects to "spawnpoint" also in the script that you create declare a variable as spawnPosition. when you die just set

transform.position = spawnPosition;