How can I access a variable that's in a StateMachineBehaviour script

Hi, can I access a variable like "speed" from a StateMachineBehaviour script through another script that is a MonoBehaviour script? I tried ScriptName sn; and then GetComponent(); and for access the speed variable i did sn.speed = 1f; but that put me only an error that i can't reference the StateMachineBehaviour script as GameObject. Then how can I access it? Or there is no way to access it ? This is my script

using UnityEngine;

 public class ScriptName : StateMachineBehaviour
 {
     public float speed;
    
 }