dolfin-convert: 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:

/usr/bin/dolfin-convert - from package: dolfin-bin

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

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