Android Game boy emulator: How to set directory in C# Script

i found a open source game boy emulator and decide port to android but im new in unity and in c# and I'm doubt this part of this code

 // Get what path to use depending on platform
     static public string getPath() {
         if (path == "") {
             // Check platforms, change this to different platfoms as needed
             // I've set SAV games and ROMs to be in the same folder.
             switch (Application.platform) {
             case (RuntimePlatform.Android):
                 path = "/accounts/1000/shared/misc/roms/gb/";
                 break;
             default:
                 path = System.Environment.CurrentDirectory + "//storage//sdcard0//Download//";
                 break;
             }
         }

how to set path to android and directory to downloads folder for example, as directory diversify as do look for another directory if not find it,It would be a variable, show me examples for this. (Sorry my english)

complete code

 using UnityEngine;
 using System.Collections;
 using System.IO;
 
 public class LoaderScript : MonoBehaviour {
 
     static public string path = "";
     static public string[] roms;
     static public int romIndex;
     static public GUIText guiText;
     static public FileInfo[] fileInfo;
 
     // Prevent long strings and show only the end of the text string
     static public string mStr(string inString) {
         int maxLen = 28;
         if (inString.Length > maxLen) {
             inString = "..." + inString.Substring(inString.Length - maxLen);
         }
         return inString;
     }
 
     // Find all the roms in the folder and display it based on romIndex
     static public void findRoms() {
 
         updateText ("Loading...");
 
         if (romIndex == null)
             romIndex = 0;
 
         string extension = "*.gb";
         DirectoryInfo dirInfo = new DirectoryInfo(getPath());
         fileInfo = dirInfo.GetFiles(extension);
 
         string tString = "";
 
         int mIndex = romIndex + 10;
         tString = "<I>" + mStr("Path: " + getPath() + "\n\n") + "</I>";
         if (fileInfo.Length > mIndex) {
             for (int i = romIndex; i < mIndex; i++) {
                 if (i == romIndex)
                     tString = tString + "> ";
                 else
                     tString = tString + "  ";
                 tString = tString + fileInfo[i].Name +"\n";
             }
             tString = tString + "... more";
         }
         else
         {
             for (int i = romIndex; i < fileInfo.Length; i++) {
                 if (i == romIndex)
                     tString = tString + "> ";
                 tString = tString + fileInfo[i].Name +"\n";
             }
             tString = tString + "... end";
         }
         tString = tString + "\n\nQ Keys WSAD [Arrows], OP [Buttons]\nSpace & Enter, T Screenshot";
 
         updateText (tString);
     }
 
     // Update our text box
     static public void updateText(string text) {
         if (guiText == null)
             guiText = GameObject.Find("Text").GetComponent<GUIText>();
         guiText.text = text;    
     }
 
     // Get what path to use depending on platform
     static public string getPath() {
         if (path == "") {
             // Check platforms, change this to different platfoms as needed
             // I've set SAV games and ROMs to be in the same folder.
             switch (Application.platform) {
             case (RuntimePlatform.BlackBerryPlayer):
                 path = "/accounts/1000/shared/misc/roms/gb/";
                 break;
             default:
                 path = System.Environment.CurrentDirectory + "\\Assets\\ROM\\";
                 break;
             }
         }
         Debug.Log("ROM path set to: " + path);
         return path;
     }
 
     // Not used
     static public void createFolder(string path) {
         Debug.Log ("Creating path: " + path);
         File.Create (path);
     }
 }