Get a float from a different GameObject? (MouseLook)

I need to access a public float from the fps controller's mouselook script. I think it is on the player? It is accessed from FirstPersonController script like it is in a drop down in the inspector. It is [Serializable]. Why doesnt this work? (im a noob and need help making a sensitivity slider and I cannot find it anywhere, if anyone has a script for that (FPSController) I would love to have it. How do i access the float? (My scirpt):

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityStandardAssets.Characters.FirstPerson;
 
 public class sensitivitySliderScript : MonoBehaviour {
     [SerializeField]
     public MouseLook m_MouseLook;
     public float xfloat;
 
 
 
     private void Start()
     {
         xfloat = MouseLook.XSensitivity;
     }
 
 
     void Update () {
 
     
 
        // PlayerPrefs.SetFloat("currentX", MouseLook.XSensitivity);
 
 
      //   MouseLook.XSensitivity = PlayerPrefs.GetFloat("currentX", 0);
 
 
 
     }
 }
 

MouseLook floats I need: using System; using UnityEngine; using UnityEngine.UI; using UnityStandardAssets.CrossPlatformInput;

 namespace UnityStandardAssets.Characters.FirstPerson
 {
     [Serializable]
     public class MouseLook
     {
    
         public float XSensitivity = 2;
         public float YSensitivity = 2;