Serialization scripting error

The modified script I am using to save, load and deletes saves of my game gives the error “Unknown identifier Convert” on line 73, could someone help me fix this?

import UnityEngine;
import System.Collections;
import System.Collections.Generic;
import System.Linq;
import Serialization;
import System.Reflection;
import System.IO.Compression;
import System.IO;
import System.Net;
import System.Collections.Generic;

var paused : boolean = false; 
var pausedGUI : GUITexture;  
var gameName : String = "Your Game";

var myList = new List.<Transform>();

function Start()
{
	if(pausedGUI)
		pausedGUI.enabled = false;
}

function Update () 
{ 
    if(Input.GetKeyUp(KeyCode.Escape))
    { 
       paused = !paused;

	    if(paused == true){
	        Time.timeScale = 0.0;
	        if(pausedGUI) pausedGUI.enabled = true;
	    } else {
	        Time.timeScale = 1.0;
	        if(pausedGUI) pausedGUI.enabled = false;
	    }
   }
}

function OnGUI() {
	if(!paused)
	{
	   GUILayout.BeginArea(Rect(200,10,400,20));
	   GUILayout.BeginVertical();
	   GUILayout.BeginHorizontal();
	   GUILayout.FlexibleSpace();
       GUILayout.FlexibleSpace();
	   GUILayout.EndHorizontal();
	   GUILayout.EndVertical();
	   GUILayout.EndArea();
	   return;
	}
	   
	var box : GUIStyle = "box";   
    GUILayout.BeginArea(Rect( Screen.width/2 - 200,Screen.height/2 - 300, 400, 600), box);

    GUILayout.BeginVertical(); 
    GUILayout.FlexibleSpace();
    if(GUILayout.Button("Save Game"))
    {
       LevelSerializer.SaveGame(gameName);
    }
    
   
    
    GUILayout.Space(60);
    for(var sg in LevelSerializer.SavedGames[LevelSerializer.PlayerName]) {
    
    if(GUILayout.Button("Deletes Save"))
    {
    LevelSerializer.SavedGames[LevelSerializer.PlayerName].Remove(sg);
    
    var data = Convert.ToBase64String(UnitySerializer.Serialize(LevelSerializer.SavedGames));
    data.WriteToFile(Application.persistentDataPath + "/saves");
    break;
    }
    
       if(GUILayout.Button(sg.Caption)) {
         LevelSerializer.LoadNow(sg.Data);
         Time.timeScale = 1;
         }
    } 
    GUILayout.FlexibleSpace();
    GUILayout.EndVertical();
    GUILayout.EndArea();


}

For Convert type add:

 using System; //for CSharp
 //or
 import System; //for Java

I hope that it will help you.