ns-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/ns-convert - from package: python-neuroshare

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

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