1st step: search mo sa google YøùTùbé to mp3 converter
2nd step: you can try ytmp3 (yung nasa unahan pag sinearch mo yung step 1)
3rd step: copy the URL then paste mo dun sa "Please insert a valid video URL
4th step: click Convert and lalabas na yung download.
May ads siya pero once lang ata na lumalabas, exit mo lang yon and okay na.