This one line Windows command does what you seem to want, to make ffmpeg (using your options above) take as its input, in turn, each flac file in the current folder and output, in the same folder, an mp3 file with the same name before the extension:
This one line Windows command does what you seem to want, to make ffmpeg (using your options above) take as its input, in turn, each flac file in the current folder and output, in the same folder, an mp3 file with the same name before the extension: