ipdb3: 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/ipdb3 - from package: python3-ipdb

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

Error in other languages:
ipdb3: bevel nie gevind nie
ipdb3: comandă negăsită
ipdb3: comando não encontrado
ipdb3: commande introuvable
ipdb3: command not found
ipdb3: käsku ei ole
ipdb3: không tìm thấy lệnh
ipdb3: komanda nerasta
ipdb3: Kommando nicht gefunden.
ipdb3: kommandot finns inte
ipdb3: komut yok
ipdb3: nie znaleziono polecenia
ipdb3: níor aimsíodh an t-ordú
ipdb3: no se encontró la orden
ipdb3: no s'ha trobat l'ordre
ipdb3: opdracht niet gevonden
ipdb3: parancs nem található
ipdb3: perintah tidak ditemukan
ipdb3: príkaz nenájdený
ipdb3: příkaz nenalezen
ipdb3: команда не найдена
ipdb3: командата не е открита
ipdb3: 命令找不到
ipdb3: コマンドが見つかりません