With this endpoint you can list all tracking info added to an order. You will need to pass order id and you’ll get respond with array of tracking numbers added to that order,

list_all_shipment_trackings.php

GET /wp-json/wc-ast/v3/orders/<order_id>/shipment-trackings/

curl -X GET https://your-domain.com/wp-json/wc-ast/v3/orders/<order_id>/shipment-trackings 
  -u consumer_key:consumer_secret 
  
  //JSON response:
  
  {
  "tracking_id": "feb9bde4475fda92cc9408607b7ecb66",
  "tracking_provider": "Fedex",
  "tracking_link": "http://www.fedex.com/Tracking?action=track&tracknumbers=12345678",
  "tracking_number": "12345678",
  "date_shipped": "2019-03-08",
  "_links": {
    "self": [
      {
        "href": "https://your-domain.com/wp-json/wc/v1/orders/340/shipment-trackings"
      }
    ],
    "collection": [
      {
        "href": "https://your-domain.com/wp-json/wc/v1/orders/340/shipment-trackings"
      }
    ],
    "up": [
      {
        "href": "https://your-domain.com/wp-json/wc/v1/orders/340"
      }
    ]
  }
}