How to load prefabs into array

There's a couple of ways to do this. The easiest would most likely be:

 public GameObject[] items;
 void Start()
 {
     // If you store all your items that you want to load in the same folder (Assets/Resources/MyItemsToLoad).
     items = Resources.LoadAll("MyItemsToLoad") as GameObject[];
 }

Then it would load all files in that folder. If you keep it to just the items that you want to load and nothing else then it would work nicely.

But if you don't want to do it like this you could do a looping solution instead.

 using System.Collections.Generic;    
 public List<GameObject> items = new List<GameObject>();
 
 void Start()
 {
     GameObject obj = null;
     int counter = 0;
     bool done = false;
     while(!done)
     {
         // We just keep loading until obj becomes null
         obj = Resources.Load("Item" + counter) as GameObject;
         if(obj == null)
             done = true; // Let's stop this now.
         else
             items.Add(obj);
         ++counter;
     }
 }

I would prefer the first solution, since I don't like to rely on errors (couldn't load) to know when you are done, but that's a matter of taste and what best suits your situation.