Question How to store ar point cloud data with positions?

Hello everyone, I want to store and access AR cloud points as mention to create separate convex hulls for different planes. I have tried couple of things but there is no luck of storing them.

Code (CSharp):

1. private void Update()
2.     {
3.         _arPointCloud = arSessionOrigin.trackablesParent.GetComponentInChildren<ARPointCloud>();
4.  
5.         if (_arPointCloud == null)
6.         {
7.             _arPointCloud = arSessionOrigin.trackablesParent.GetComponentInChildren<ARPointCloud>();
8.         }
9.         else
10.         {
11.             if (_arPointCloud.confidenceValues.GetValueOrDefault().IsCreated)
12.             {
13.                 _featurePoints = new List<Vector3>(_arPointCloud.positions);
14.             }
15.         }
16.        
17.         if (_arPointCloud.positions.HasValue)
18.         {
19.             text.text = "Length : " + _featurePoints.Count;
20.         }
21.     }

How should I proceed to achieve this?