I'm usually able to manage it with
for i in *.mpg3;do ffmpeg -i "$i" -vol 500 "$"{i%%.mp3}".mp3;done
Or similar. Main point being put the first "$i" in quotes and the second $"{iWhatever}" in quotes as well.
I just tried, after reproducing that mp3 name.
Code:
for i in *.mp3; do mv "$i" "${i%%.mp3}".1mp3;done
(I didn't have the actual mp3 and so just touched a file with the name, as well as my test.mp3, then renamed them.)
ls *mp3
13_2 - All The Way (Duet With Frank Sinatra).1mp3 my test.1mp3