Help i get this error Assets/MouseManager.cs(11,20): error CS1525: Unexpected symbol `{'

using UnityEngine;
using System.Collections;

public class MouseManager : MonoBehaviour {

void Update() {
	if( Input.GetMouseButtonDown (0)
	    // We clicked, but on what?

    
	   {Vector3 mouseWorldPos3D = Camera.main.ScreenToWorldPoint(Input.mousePosition)
	    Vector2 mousePos2D = new Vector2(Input.mouseWorldPos3D.x, Input.mouseWorldPos3D.y)}

	    Vector2 dir = Vector2.zero;

	    RaycastHit2D hit = Physics2D.Raycast (mousePos2D, dir);
	    if(hit != null && hit.collider!=null) {
	       // We clicked on SOMETHING that has a collider
	       if(hit.collider.rigidbody2D !=null) {
	           hit.collider.rigidbody2D.gravityScale = 1;
		  }
	  }
  }

}

I’m not sure where was your original problem as this script had soo many error.
You should declare Vector2 mousePos2D outside the if() otherwise you can’t use its value in the Raycast. You were missing a couple of " ; "
“hit !=null” always returns true use “hit” instead

using UnityEngine; 
using System.Collections;

public class MouseManager : MonoBehaviour {

	Vector2 mousePos2D;

	void Update() {
		if( Input.GetMouseButtonDown (0)){
			Vector3 mouseWorldPos3D = Camera.main.ScreenToWorldPoint(Input.mousePosition);
			mousePos2D = new Vector2(mouseWorldPos3D.x, mouseWorldPos3D.y);
		}
		
		Vector2 dir = Vector2.zero;
		RaycastHit2D hit = Physics2D.Raycast (mousePos2D, dir);
		if(hit && hit.collider && hit.collider.GetComponent<Rigidbody2D>() != null) {
			hit.collider.GetComponent<Rigidbody2D>().gravityScale = 1;
		}
	}
}