How can i pick up object is an order

If I understand your question you're trying to pick up objects in an order and once all the items have been picked up (in the correct order) then you want to open a door.

Assuming I understand correctly, how about something like the following:

 public int TotalObjects; //there are more elegant ways to get this number but for this is just proof-of-concept
 
 int _itemsPickedUp = 0;
 bool _allItemsPickedUpInOrder = true;
 
 public void PickUpObject(YourFancyGameObject obj) {
    //in the object that you're picking up, have a public field that indicates what its order number is and compare it to the currently picked up items
    //this assumes zero-index
    if(obj.itemOrder != _itemsPickedUp) {
       _allItemsPickedUpInOrder = false;
    }
    
    _itemsPickedUp++; //increment when you pick up an object
    
    //if all items have been picked up
    if(_itemsPickedUp == TotalObjects) {
       //and all items were picked up in order
       if(_allItemsPickedUpInOrder) {
          OpenDoor(); //call the open door function
       } else {
          //if they weren't picked up in order
          //display message to user or reset objects?
       }
    }
 }

Easiest way is to create a tag, e.g. "doorKey", tag all those objects needed to be picked and run a simple script.

 var doorKeys: GameObject[];
 var openDoor: boolean;

 function Update()
 {
      doorKeys = gameObject.FindGameObjectsWithTag("doorKey");
 
       if(doorKeys.length == 0)
       {
               openDoor = true;
       }
 }