How to resolve the error
This error occurs because you did not convert when you had this project opened in Unity 5.
When you open a project from an old version of Unity, it will say that there are some obsolete things and ask if you want to convert to the latest one. When it does not convert it keeps the old structure, which eventually results in error in some cases.
The error you marked is about how to work with the Particle system.
In the old days you could make a direct call from him as you marked in yellow, now you need to call the Getcomponent.
http://docs.unity3d.com/Manual/class-ParticleSystem.html
Your code would look like this
using UnityEngine;
using System.Collections;
public class RandomParticlePoint : MonoBehaviour
{
[Range(0f, 1f)]
public float normalizedTime;
void OnValidate()
{
GetComponent<ParticleSystem>().Simulate (normalizedTime, true, true);
}
}
How to add the component
For your code to work GetComponent
the object on which you hung your script also needs to have the component you are asking for.
Here’s a video teaching how to work with the component Particle System
https://www.youtube.com/watch?v=Y-Kl5jQ2A8k