How do I join multiple audio files into one with regular delays in between using FFMPEG?

I have the following audio files in my folder:

01.mp4
02.mp4
03.mp4
04.mp4
...
27.mp4

They’re all audio-only files. I want to use FFMPEG to concatenate them with a 3-second spacing/silent pause in between each track. The files are of different lengths btw. I have tried to use

ffmpeg -i "concat:01.mp4|02.mp4|03.mp4|04.mp4|05.mp4|06.mp4|07.mp4|08.mp4|09.mp4|10.mp4|11.mp4|12.mp4|13.mp4|14.mp4|15.mp4|16.mp4" -filter_complex "[0:a]apad=pad_dur=3[aout]" -map "[aout]" output.mp4

but it only copied 01.mp4 with an added 3-second silence at the end.

How can I achieve this in Windows cmd Command Prompt, preferably in one line?