publish pos_rot message of a cube from Unity3D to ROS side but convert the co-ordinate frame and then publish the message so that Gazebo and Unity simulation looks exactly identical

RosPublisherExample.cs

using UnityEngine;
using Unity.Robotics.ROSTCPConnector;
using RosMessageTypes.UnityRoboticsDemo;
using Unity.Robotics.ROSTCPConnector.ROSGeometry;
using Unity.Robotics.UrdfImporter;
using RosMessageTypes.Geometry;
/// <summary>
///
/// </summary>
public class RosPublisherExample : MonoBehaviour
{
    ROSConnection ros;
    public string topicName = "pos_rot";

    // The game object
    public GameObject cube;
    // Publish the cube's position and rotation every N seconds
    public float publishMessageFrequency = 0.5f;

    // Used to determine how much time has elapsed since the last message was published
    private float timeElapsed;
   
    void Start()
    {
        // start the ROS connection
        ros = ROSConnection.instance;
        ros.RegisterPublisher<PosRotMsg>(topicName);
        ros.RegisterPublisher<PosRotMsg>("new_pos_rot");
        
    }

    private void Update()
    {
        timeElapsed += Time.deltaTime;

        if (timeElapsed > publishMessageFrequency)
        {
            cube.transform.rotation = Random.rotation;

            PosRotMsg cubePos = new PosRotMsg(
                cube.transform.position.x, 
                cube.transform.position.y,    
                cube.transform.position.z,
                cube.transform.rotation.x,
                cube.transform.rotation.y,
                cube.transform.rotation.z,
                cube.transform.rotation.w
            );
       
            
            Vector3<FLU> rosPos = cube.transform.position.To<FLU>();
         
            Quaternion<FLU> rosPos2=cube.transform.rotation.To<FLU>();

            PosRotMsg msg = new PosRotMsg();
            msg.pos_x=rosPos.x;
            msg.pos_y=rosPos.y;
            msg.pos_z=rosPos.z; 
            msg.rot_x = rosPos2.x;
            msg.rot_y = rosPos2.y;
            msg.rot_z = rosPos2.z;
            msg.rot_w = rosPos2.w;         
            


            ros.Send("new_pos_rot", msg);

            timeElapsed = 0;
        }
    }
}