xmdump3: 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/xmdump3 - from package: med-tools

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

On Debian possible default full paths are:

/usr/bin/xmdump3 - from package: libmed-tools

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

Error in other languages:
xmdump3: bevel nie gevind nie
xmdump3: comandă negăsită
xmdump3: comando não encontrado
xmdump3: commande introuvable
xmdump3: command not found
xmdump3: käsku ei ole
xmdump3: không tìm thấy lệnh
xmdump3: komanda nerasta
xmdump3: Kommando nicht gefunden.
xmdump3: kommandot finns inte
xmdump3: komut yok
xmdump3: nie znaleziono polecenia
xmdump3: níor aimsíodh an t-ordú
xmdump3: no se encontró la orden
xmdump3: no s'ha trobat l'ordre
xmdump3: opdracht niet gevonden
xmdump3: parancs nem található
xmdump3: perintah tidak ditemukan
xmdump3: príkaz nenájdený
xmdump3: příkaz nenalezen
xmdump3: команда не найдена
xmdump3: командата не е открита
xmdump3: 命令找不到
xmdump3: コマンドが見つかりません