ffmpeg add loop to this line of code i have
You want to take a look at the aloop-filter.

ffmpeg -i "song.mp4" -i "2.mp3" -filter_complex "[1:a]aloop=loop=-1[al];[al]adelay=3000|60000[1a];[0:a][1a]amix" -vcodec copy -y "output1.mp4"


https://ffmpeg.org/ffmpeg-filters.html#aloop

And then you will probably want to limit the song.mp4, so we are using the duration option of amix, to tell it to limit by the first input given. https://ffmpeg.org/ffmpeg-filters.html#amix

ffmpeg -i "song.mp4" -i "2.mp3" -filter_complex "[1:a]aloop=loop=-1[al];[al]adelay=3000|60000[1a];[0:a][1a]amix=duration=first" -vcodec copy -y "output1.mp4"


Since I am not sure which of the two files you want to loop and don't know if you want to loop before or after the delay you might need to adjust the order of filters.