Add all music to the playlist-select full right-click format conversion-a dialog box appears: automatically add the serial number to the file, and the converted song name will be preceded by the serial number.

Note: when the format is converted again, it is best to rebuild a folder and set the converted song directory in this folder; If you have many song files, you'd better set the output file format to WMA, so that the converted file size will be smaller than the original and the speed will be relatively faster. You can also choose MP3 format for personal selection.