Please don’t post screenshots of code, as it makes it difficult for anyone else to read/modify it. There’s an Insert Code feature specifically for this purpose. See this stickied topic for more information.
As for your question (which you haven’t really elaborated on; please also avoid this in the future!):
You already have an array of GameObjects, and so all you need to do is generate a random index (integer) to plug into that array. A random index plugged into an array equals a random element from that array!
In your specific case, here’s a method that would achieve just that:
private void ActivateRandomLevel()
{
int randomLevel;
// Keep generating a random level number until you get one that isn't the current level's
do
{
randomLevel = Random.Range(0, Levels.Length);
}
while (randomLevel == currentLevel);
// Assign the current level's number to the newly-generated one
currentLevel = randomLevel;
// Activate the new level
Levels[currentLevel].SetActive(true);
}
And so instead of doing this in your original code:
currentLevel++;
Levels[currentLevel].SetActive(true);
You would replace those two lines with a single call to the method above:
ActivateRandomLevel();