Enter "services.msc" on the Start menu search box.
Find MySQL service under Name column, for example, MySQL56.
Right click on MySQL service, and select Properties menu.
Look for "Path To Executable" under General tab, and there is your .ini file, for instance, "C:\Program Files (x86)\MySQL\MySQL Server 5.6\bin\mysqld.exe" --defaults-file="C:\ProgramData\MySQL\MySQL Server 5.6\my.ini" MYSQL56