Convert PC horizontal controls to mobile buttons left/right input

Unity Engine
, ,
1

A while back I’ve made a PC endless runner game. Now I want to convert to mobile but I cannot wrap my head around how to convert the controls from A/D to left/right buttons for mobile
This is the script which controlls the player:

    public float speed = 1;
    public float maxSpeed;
    public Rigidbody rb;
    public bool PlayerIsAlive;
    public Vector3 movement;
    public SpawnManager spawnManager;
  
    // Start is called before the first frame update
    void Start()
    {
      
        PlayerIsAlive = true;
        rb = this.GetComponent<Rigidbody>();
    }

 

    void FixedUpdate()
    {
      
        moveCharacter(movement);
        movement = new Vector3(Input.GetAxis("Horizontal"), 0, 1.9f);
        movement = Vector3.ClampMagnitude(movement, 1);

    }
    public void moveCharacter(Vector3 direction)
    {
        rb.MovePosition(transform.position + (direction * speed * Time.deltaTime));
    }
   
    private void OnTriggerEnter(Collider other)
    {
        spawnManager.SpawnTriggerEntered();
    }