how to re-scale guiStyle property as per screen resolution?

First, create a Vector3, lets call it Scale where the X will be the screen.width/your_resolution_width_Objective, the Y will be the screen.height/your_resolution_height_objective, and the Z will be 1.

Then multiply all of your GUI sizes width Scale.X , GUI sizes height Scale.Y.

For the font you will create a variable float and lets call it NewFontSize, you will multiply the currentFontSize * Scale.X, and then assign to scoreStyle.fontSize the NewFontSize, in this way the font will be scale.

This is a sample code:

 using UnityEngine;
 using System.Collections;
 
 public class ScaleAllGUI : MonoBehaviour {
 
     public float originalWidth = 768.0f;
     public float originalHeight = 1024.0f;
     private Vector3 Scale = new Vector3(0,0,0);
 
     // Use this for initialization
     void Start () {
 
         Scale.x = (float)Screen.width/originalWidth;
         Scale.y = (float)Screen.height/originalHeight; // calculate vert scale
         Scale.z = 1;
     
     }
 
     //ALWAYS MULTIPLY YOUR REAL GUI WIDTH OF EACH OBJECT * SCALE.X AND YOUR REAL GUI HEIGHT OF EACH OBJECT * SCALE.Y
     void OnGUI()
     {
         //Put all your GUI here (button,label,toggle,etc)
         if(GUI.Button(new Rect(Your_position_on_x, Your_position_on_y, The_width_of_this_gui * Scale.x, The_height_of_this_gui * Scale.y),Your_texture))
         {
         }
 
         GUI.Label(new Rect(Your_position_on_x, Your_position_on_y, The_width_of_this_gui * Scale.x, The_height_of_this_gui * Scale.y),Your_texture);
 
 
         //Now for the font one, we create a variable and we multiply the fontSize of the style * Scale.x
         float NewFontSize = Scale.x * current_font_size_of_your_style;
         scoreStyle.fontSize = (int)NewFontSize;
 
         GUI.Label(screenRect(0.0f,10.0f,246.0f * Scale.x,146.0f * Scale.y),m_distance.ToString() + " mnn" + m_score.ToString(), scoreStyle);
 
 
     }
 
 }