Save as many pickables as you want to

Hi guys So I started to play around with the save and load problem in unity. I'm using PlayerPrefs at the moment, and my question is: Is there a way to save as much pickable objects as you want? So for example I have 5 different keys, which the player can pick up. But since a good script is modular, if I have 15 keys in the next level, I dont want to add another 10 lines into the saving function to save them. I'm thinking about arrays, but have no idea how to do it. So what I really want to do is, that each key would check when loading up the game, if it was picked up before. If yes, then disable that key, if not then enable it. Thanks in advance :)