If you're on Windows, you may find the config file my.ini
it in this directory
C:\ProgramData\MySQL\MySQL Server 5.7\
You open this file in a text editor and look for this section:
# The TCP/IP Port the MySQL Server will listen on
port=3306
Then you change the number of the port, save the file. Find the service MYSQL57 under Task Manager > Services and restart it.