How do I make my character move on the Z axis on 2d rigidbody?

Im using rigidbody2ds velocity feature for movement and i need to move my character on the Z axis, problem is I cant figure out how to enable the Z axis for rigidbody 2d. It's a topdown roguelike sprite game with movement similar to binding of isaac. This is my current script.

  using UnityEngine;
  
  /// <summary>
  /// Player controller and behavior
  /// </summary>
  public class PlayerScript : MonoBehaviour
  {
      /// <summary>
      /// 1 - The speed of the ship
      /// </summary>
      public Vector3 speed = new Vector3(50, 50, 50);
  
      // 2 - Store the movement and the component
      private Vector3 movement;
      private Rigidbody2D rigidbodyComponent;
  
      void Update()
      {
          // 3 - Retrieve axis information
          float inputX = Input.GetAxis("Horizontal");
          float inputZ = Input.GetAxis("Vertical");
          float inputY = Input.GetAxis("Y");
  
          // 4 - Movement per direction
          movement = new Vector3(
            speed.x * inputX,
            speed.y * inputY,
            speed.z * inputZ);
  
          // ...
  
          // 5 - Shooting
          bool shoot = Input.GetButtonDown("ArrowRight");
          bool shootup = Input.GetButtonDown("ArrowUp");
          bool shootdown = Input.GetButtonDown("ArrowDown");
          bool shootleft = Input.GetButtonDown("ArrowLeft");
          // Careful: For Mac users, ctrl + arrow is a bad idea
  
          if (shootdown)
          {
              WeaponScriptDown weaponup = GetComponent<WeaponScriptDown>();
              if (weaponup != null)
              {
                  // false because the player is not an enemy
                  weaponup.Attack(false);
              }
          }
          if (shootleft)
          {
              WeaponScriptLeft weaponup = GetComponent<WeaponScriptLeft>();
              if (weaponup != null)
              {
                  // false because the player is not an enemy
                  weaponup.Attack(false);
              }
          }
          if (shootup)
          {
              WeaponScriptUp weaponup = GetComponent<WeaponScriptUp>();
              if (weaponup != null)
              {
                  // false because the player is not an enemy
                  weaponup.Attack(false);
              }
          }
          if (shoot)
          {
              WeaponScript weapon = GetComponent<WeaponScript>();
              if (weapon != null)
              {
                  // false because the player is not an enemy
                  weapon.Attack(false);
              }
          }
  
          // ...
  
      }
  
  
      void FixedUpdate()
      {
          // 5 - Get the component and store the reference
          if (rigidbodyComponent == null) rigidbodyComponent = GetComponent<Rigidbody2D>();
  
          // 6 - Move the game object
          rigidbodyComponent.velocity = movement;
  
          // 7 - Z axis in rigidbody
          
      }
  }