In 3.0.x the answers you provide to each installation prompt are saved, to avoid you having to re-enter the same information over and over, so you need to edit the file where these settings are stored, see here:
Note that the listen port is stored in the standalone mode configuration file (along with the static resources path), and you will not be re-prompted to enter it if that file exists and contains the port setting.
If you want to change the listen port after setup you can use the standalone command to modify it.
For example if I wanted to change the listen port to 8087 then I would do:
java -jar ords.war standalone --port 8087
This will start standalone mode listening on port 8087, the updated port value will be stored in the configuration file