Instantiate object in scene Unity (GUI)

gui.cs

var canvas3D = FindCanvas3D();
if (canvas3D == null) throw new System.Exception(TODO);
var gizmo = Instantiate(Resources.Load<GameObject>("GizmoLine"));
gizmo.transform.SetParent(canvas3D.transform);
gizmo.transform.localScale = TODO;


static Canvas FindCanvas3D() {
    var canvas = FindObjectsOfType<Canvas>();
    foreach (var c in canvas) {
        if (c.name == "Canvas3D") return c;
    }
    return null;
}