thanks for the help UFHH01, I found the nginx config that is listen to ports (80 and 443) and proxy then to (7080 and 7081) at
/etc/nginx/plesk.conf.d/server.conf
however at the header of the file content, I got this:
#ATTENTION!
#
#DO NOT MODIFY THIS FILE BECAUSE IT WAS GENERATED AUTOMATICALLY,
#SO ALL YOUR CHANGES WILL BE LOST THE NEXT TIME THE FILE IS GENERATED.
...so should I ignore this alert and change the ports? or is there another way?