How to transform vision framework coordinate system into ARKit?

I am using ARKit (with SceneKit) to add the virtual object (e.g. ball). I am tracking real world object (e.g. foot) by using Vision framework and receiving its updated position in vision request completion handler method.

let request = VNTrackObjectRequest(detectedObjectObservation: lastObservation, completionHandler: self.handleVisionRequestUpdate)

I wants to replace the tracked real world object with virtual (for example replace foot with cube) but I am not sure how to replace the boundingBox rect (which we receive in vision request completion) into scene kit node as coordinate system are different.

below is the code of vision request completion handler:

 private func handleVisionRequestUpdate(_ request: VNRequest, error: Error?) {
    // Dispatch to the main queue because we are touching non-atomic, non-thread safe properties of the view controller
    DispatchQueue.main.async {
      // make sure we have an actual result
      guard let newObservation = request.results?.first as? VNDetectedObjectObservation else { return }

      // prepare for next loop
      self.lastObservation = newObservation

      // check the confidence level before updating the UI
      guard newObservation.confidence >= 0.3 else {
        return
      }

      // calculate view rect
      var transformedRect = newObservation.boundingBox

     //How to convert transformedRect into AR Coordinate
  self.node.position = SCNVector3Make(?.worldTransform.columns.3.x,
    ?.worldTransform.columns.3.y,

    }
  }

Please guide me to transfer the coordinate system.