FFmpeg is the ideal command-line tool for these tasks.
ffmpeg -i "rick_and_morty_s03e01.mkv" -c copy "rick_and_morty_s03e01.mp4" rick and morty s03e01 ffmpeg
ffmpeg -i "s03e01.mkv" -map 0:a:0 -c:a mp3 -b:a 192k rick_speech.mp3 FFmpeg is the ideal command-line tool for these tasks