CSHARP

instantiate scale object

GameObject newObject = Instantiate(objectPrefab, location, Quaternion.identity) as GameObject;  // instatiate the object
newObject.transform.localscale = new Vector3(whatever.x, whatever.y, whatever.z); // change its local scale in x y z format

Instantiate objects scale

public GameObject objectPrefab; // whatever you want to instantiate
public Vector3 location; // place you want it
 
GameObject newObject = Instantiate(objectPrefab, location, Quaternion.identity) as GameObject;  // instatiate the object
newObject.transform.localScale = new Vector3(whatever.x, whatever.y, whatever.z); // change its local scale in x y z format