How to save Slider fill area in Xml?

I have been trying for days to make a saving system that can save the player settings. My only problem is that when a player has tweaked the sound settings and reopen the game. Then the game will load the saved volume, but the Slider will be reset. So My problem is How can I save the Volume and the slider fill area, and be able to load at the start of the game?

I thought of maybe trying to save these values, except for Pos Z And when starting the game it just has to load these 4 values back in the Slider Fill area. Don't know if it is a good idea, and I don't know if these values are floats or vectors.

My script so far:

 public void SaveSettingsData()
 {
     SaveManagerPlayerPreferences.instance.activeSettingsSave.masterVolume = currentVolumeForMaster;
 
     SaveManagerPlayerPreferences.instance.SavePlayerPreferences();    //Instance Save
 }
 void Start()
 {
 
     if (System.IO.File.Exists(Application.persistentDataPath + "/" + SaveManagerPlayerPreferences.instance.activeSettingsSave.saveName + ".preferencesSave"))
     {
         newVolumeForMaster = SaveManagerPlayerPreferences.instance.activeSettingsSave.masterVolume;
         ChangeMasterVolume(newVolumeForMaster);
 
     }
 }
 public void ChangeMasterVolume(float newVolume)
 {
     audioMixer.SetFloat("MasterVolume", Mathf.Log10(newVolume) * 20);
 }

Any help will be much appreciated! Thank you for reading this.