It is not recommended to change the default Plesk port because it can break Plesk integration with other programs like Plesk Expand or DrWeb.
To change the port Plesk listens on you will need to edit /usr/local/psa/admin/conf/httpsd.conf file and change the following directives to list the port you want Plesk to listen on:
You will need to restart Plesk afterwards. Plesk cannot listen on any of the ports used for common services.
Most Plesk installs will be using Apache by default. You will want to edit the Apache configuration file C:\Program Files\SWsoft\Plesk\admin\conf\httpd.conf
1.) Change the following line to list the port number you want Plesk to listen on
2.) Restart Plesk Control Panel.