convert..switch: 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 Debian possible default full paths are:

/var/lib/wims/public_html/bin/convert..switch - from package: wims

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

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