How do I change the scene after 2 objects are destroyed (SetActive false)

Sorry, this may be a beginner question but I’m having trouble changing the scene after two objects are destroyed (set active false) I have a game where the goal is to shoot all of the targets. I want it so that when the 2 objects disappear, the player proceeds to the next scene/next level. The actual scene change works, just not the if statement.
Here is my current script:

void Start () 
{
	
}

void Update () 
{
	if (gameObject.SetActive (false))
		{
			SceneManager.LoadScene ("Level2");
		}
}

(By the way, I have the lines before the void Start thing all fine)

When I run this script an error message like this shows up next to the “if (gameObject.SetActive (false))” line:

Cannot implicitly convert type ‘void’ to ‘bool’

This message points to the S in “SetActive” on that line.

I’m new to this scripting stuff so I don’t know what these error messages mean. I know it’s probably really easy but thanks in advance!

check gameObject.activeInHierarchy in the condition.
GameObject.activeInHierarchy represents if the object is active within the entirety of the scene. An object can be made inactive if their gameobject or any of their parent’s gameobjects have been set to inactive.

if (gameObject.activeInHierarchy)
         {
             SceneManager.LoadScene ("Level2");
         }