Note: 
Backup your files and database before upgrade.

Updation Steps:

1) Delete this folder from your server completely
->  "/admin/exploder/"

2) Goto this folder: "/Upgrade/v2.9 to v3.0/Upload"

3) Use your Server FTP or File Manager application on your server. 

4) Now, replace old files directly with new files present at upload directory.

5) Execute "upgrade.php" file.

Example:
https://your-website.com/upgrade.php

You have done the work!