Version 3 is a standalone PHP application, not a WordPress plugin. It is installed fresh: settings, pages, posts and download history from 2.x are not migrated. It requires PHP 8.2 or newer (2.x ran on PHP 7.4).
Keep your 2.x site running while you set up version 3.
Install version 3 in a subfolder or on a subdomain (see Installing on cPanel).
Set it up: site name, logo, colours, languages, ads and platforms (see First Steps After Installation).
Recreate the pages and blog posts you want to keep by copying them from WordPress. Landing pages for every platform are created automatically in 9 languages.
When you are happy with it, back up and remove the WordPress installation, then move version 3 into the main folder or point the domain to it.
Platform landing pages have new addresses (for example /en/youtube-video-downloader/). If your old pages rank well in search engines, add 301 redirects from the old addresses in .htaccess or your NGINX configuration.
If the site moves to another domain, set 'canonical_host' => 'new-domain.com' in config/config.local.php.