unitconv: command not found

Have You tried accessing the binary with the full path?

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/unitconv - from package: xcrysden

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