sfconvert: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/sfconvert - from package: audiofile

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/sfconvert - from package: audiofile-tools

You may install the required package with command apt-get install {package}

Error in other languages:
sfconvert: bevel nie gevind nie
sfconvert: comandă negăsită
sfconvert: comando não encontrado
sfconvert: commande introuvable
sfconvert: command not found
sfconvert: käsku ei ole
sfconvert: không tìm thấy lệnh
sfconvert: komanda nerasta
sfconvert: Kommando nicht gefunden.
sfconvert: kommandot finns inte
sfconvert: komut yok
sfconvert: nie znaleziono polecenia
sfconvert: níor aimsíodh an t-ordú
sfconvert: no se encontró la orden
sfconvert: no s'ha trobat l'ordre
sfconvert: opdracht niet gevonden
sfconvert: parancs nem található
sfconvert: perintah tidak ditemukan
sfconvert: príkaz nenájdený
sfconvert: příkaz nenalezen
sfconvert: команда не найдена
sfconvert: командата не е открита
sfconvert: 命令找不到
sfconvert: コマンドが見つかりません