counting score after destroying game object

Hi.
I just can’t get it working. I tried to see other solutions but I can’T see what I did wrong.

I have a simple game where you just avoid obstacles. Those obstacles travel towards the player (cube). Behind the player I have wall that on collision testroyes obstacle.

I added 3d text and I just don’t know how to set it to count score.

void OnCollisionEnter(Collision col)
{
    if (col.gameObject.name == "Obstacle(Clone)")
    {
        Destroy(col.gameObject);
    }
}

Have many ways. Try a basic tutorial to get the skill to read a code.

Official Unity Tutorial - Survival Shooter - Scoring Points