Help using arrow keys to move

i have the following code, in this code we move the object left and right, what i am trying to do is to move our object right left and middle with just left and right arrow key. i am new kindly help me out. Regards

#pragma strict

public var smooth : float;

private var newPosition : Vector3;
private var newIntensity : float;
private var newColour : Color;


function Awake ()
{
    newPosition = transform.position;
  
}


function Update ()
{
    PositionChanging();
  
}


function PositionChanging ()
{
    var positionM : Vector3 = new Vector3(39.90576,1.292813,1.095224);
    var positionR : Vector3 = new Vector3(39.90576,1.292813,7.095224);
    var positionL : Vector3 = new Vector3(39.90576,1.292813,-3.095224);
        
    if(Input.GetKeyDown("right"))
        newPosition = positionR;
    if(Input.GetKeyDown("left"))
        newPosition = positionL;
    
    transform.position = Vector3.Lerp(transform.position, newPosition, smooth * Time.deltaTime);
    ssDebug.Log("v@ " +transform.position);
}

if(transform.position==positionR)
{
if(Input.GetKeyDown(“left”))
newPosition = positionM;
}
else if(transform.position==positionM)
{
if(Input.GetKeyDown(“left”))
newPosition = positionL;
if(Input.GetKeyDown(“right”))
newPosition = positionR;
}
else if(transform.position==positionL)
{
if(Input.GetKeyDown(“right”))
newPosition = positionM;
}

it should work if I understood your question
first you have to check which position it is and then move it from that position.