Not Able to Convert 2D trajectory(right Side) into 3dTrajectory(forward Direction)...

Hi,

I have made one demo of archery type game, in that i have written code for trajectory in 2d space(from many reference) and it is displayed in left-right direction, but same thing, i want to do for forward-backward direction (3d Space), i have tried to set z vlaues of position as well as rotation, but can't get in right way.

The below code is working for 2d trajectory, Please help me how do i make it workable for 3d space also.

Thank You.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class BoweasyLevel : MonoBehaviour 
 {
     private List<GameObject> trajectoryPoints;
     public GameObject TrajectoryPointPrefeb;
     private GameObject ball;
     
     private float power = 25;
     private int numOfTrajectoryPoints = 30;
     
     
     public GameObject arrowPrefab;
     //Clone of the bullet
     GameObject Clone;
     
     Vector2 mousePos;
     Vector3 screenPos;
     bool  isDragged;
     bool fired;
     public float hSliderValue = 10.0f;
     
     void Start()
     {
         mousePos = new Vector2 ();
         screenPos = new Vector3 ();
         fired = false;
         isDragged = false;
         hSliderValue = 10f;
         
         trajectoryPoints = new List<GameObject>();
         for(int i=0;i<numOfTrajectoryPoints;i++)
         {
             GameObject dot= (GameObject) Instantiate(TrajectoryPointPrefeb);
             dot.renderer.enabled = false;
             trajectoryPoints.Insert(i,dot);
         }
     }
     
     void  Update (){
         if(Input.GetMouseButtonDown(0))
         {
             Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
             RaycastHit hit;
             if (Physics.Raycast(ray, out hit, 100))
             {
                 if(hit.transform.gameObject.name == "bow")
                 {
                     
                     if(!isDragged)
                     {
                         isDragged = true;
                     }
                 }
             }
         }
         if(Input.GetMouseButtonUp(0))
         {
             
             if(isDragged)
             {
                 isDragged = false;
                 FireBullet();
             }
             
         }
         if(isDragged)
         {
             mousePos = Input.mousePosition;
             screenPos = Camera.main.ScreenToWorldPoint(new Vector3(mousePos.x, mousePos.y, transform.position.z - Camera.main.transform.position.z));
             
             float temp_Z = Mathf.Atan2((screenPos.y - transform.position.y), (screenPos.x - transform.position.x))*Mathf.Rad2Deg;
             //if(temp_Z>=-10 && temp_Z<=90)
             //{
             transform.eulerAngles = new Vector3(0, 0, temp_Z);
             
             setTrajectoryPoints(transform.position, transform.TransformDirection(Vector3.right * hSliderValue));
         }
         if (fired && !Clone.GetComponent<stickMe>().isSticked) {
             Debug.Log("Done");
             
             Vector3 vel =  Clone.rigidbody.velocity;
             float angle = Mathf.Atan2(vel.y,vel.x)*Mathf.Rad2Deg;
             
             print(angle);
             Clone.transform.eulerAngles = new Vector3(0, 0, angle);
         }
     }
     
     
     void OnGUI() {
         hSliderValue = GUILayout.VerticalSlider(hSliderValue, 10.0f, 20.0f);
         GUILayout.Label("Force : "+hSliderValue.ToString());
         GUI.Label (new Rect(Screen.width/2-75,50,150,50),Application.loadedLevelName);
     }
     
     public void FireBullet(){
         
         fired = true;
         Clone = Instantiate(arrowPrefab, transform.position + new Vector3(0f,0f,1f), transform.rotation) as GameObject;
         print (Clone.transform.position.z);
         Clone.rigidbody.velocity = transform.TransformDirection(Vector3.right * hSliderValue);
         
     }
 
     void setTrajectoryPoints(Vector3 pStartPosition , Vector3 pVelocity )
     {
         float velocity = Mathf.Sqrt((pVelocity.x * pVelocity.x) + (pVelocity.y * pVelocity.y));
         float angle = Mathf.Rad2Deg*(Mathf.Atan2(pVelocity.y , pVelocity.x));
         float fTime = 0;
         
         fTime += 0.1f;
         for (int i = 0 ; i < numOfTrajectoryPoints ; i++)
         {
             float dx = velocity * fTime * Mathf.Cos(angle * Mathf.Deg2Rad);
             float dy = velocity * fTime * Mathf.Sin(angle * Mathf.Deg2Rad) - (Physics2D.gravity.magnitude * fTime * fTime / 2.0f);
             Vector3 pos = new Vector3(pStartPosition.x + dx , pStartPosition.y + dy ,2);
             trajectoryPoints[i].transform.position = pos;
             trajectoryPoints[i].renderer.enabled = true;
             trajectoryPoints[i].transform.eulerAngles = new Vector3(0,0,Mathf.Atan2(pVelocity.y - (Physics.gravity.magnitude)*fTime,pVelocity.x)*Mathf.Rad2Deg);
             fTime += 0.1f;
         }
     }
 }