To answer the original question:

To change the XAMPP Apache server port here the procedure :

1. Choose a free port number

The default port used by Apache is 80.

Take a look to all your used ports with Netstat (integrated to XAMPP Control Panel).

Then you can see all used ports and here we see that the 80port is already used by System.

Choose a free port number (8012, for this exemple).

2. Edit the file “httpd.conf“

This file should be found in C:\xampp\apache\conf on Windows or in bin/apache for Linux.:

Listen 80
ServerName localhost:80

Replace them by:

Listen 8012
ServerName localhost:8012

Save the file.

Access to : http://localhost:8012 for check if it’s work.

If not, you must to edit the http-ssl.conf file as explain in step 3 below. ↓

3. Edit the file “http-ssl.conf“

This file should be found in C:\xampp\apache\conf\extra on Windows or see this link for Linux.

Locate the following lines:

Listen 443
<VirtualHost _default_:443>
ServerName localhost:443

Replace them by with a other port number (8013 for this example) :

Listen 8013
<VirtualHost _default_:8013>
ServerName localhost:8013

Save the file.

Restart the Apache Server.

Access to : http://localhost:8012 for check if it’s work.

4. Configure XAMPP Apache server settings

If your want to access localhost without specify the port number in the URL
http://localhost instead of http://localhost:8012.

• Open Xampp Control Panel
• Go to Config ► Service and Port Settings ► Apache
• Replace the Main Port and SSL Port values ​​with those chosen (e.g. 8012 and 8013).
• Save Service settings
• Save Configuration of Control Panel
• Restart the Apache Server
  
  It should work now.

4.1. Web browser configuration

If this configuration isn’t hiding port number in URL it’s because your web browser is not configured for. See : Tools ► Options ► General ► Connection Settings… will allow you to choose different ports or change proxy settings.

4.2. For the rare cases of ultimate bad luck

If step 4 and Web browser configuration are not working for you the only way to do this is to change back to 80, or to install a listener on port 80 (like a proxy) that redirects all your traffic to port 8012.

To answer your problem :

If you still have this message in Control Panel Console :

Apache Started [Port 80]

• Find location of xampp-control.exe file (probably in C:\xampp)
• Create a file XAMPP.INI in that directory (so XAMPP.ini and xampp-control.exe are in the same directory)

Put following lines in the XAMPP.INI file:

[PORTS]
apache = 8012

Now , you will always get:

Apache started [Port 8012]

Please note that, this is for display purpose only.
It has no relation with your httpd.conf.