squid3: 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/lib/debug/usr/sbin/squid3 - from package: squid3-dbg
/usr/sbin/squid3 - from package: squid3

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

Error in other languages:
squid3: bevel nie gevind nie
squid3: comandă negăsită
squid3: comando não encontrado
squid3: commande introuvable
squid3: command not found
squid3: käsku ei ole
squid3: không tìm thấy lệnh
squid3: komanda nerasta
squid3: Kommando nicht gefunden.
squid3: kommandot finns inte
squid3: komut yok
squid3: nie znaleziono polecenia
squid3: níor aimsíodh an t-ordú
squid3: no se encontró la orden
squid3: no s'ha trobat l'ordre
squid3: opdracht niet gevonden
squid3: parancs nem található
squid3: perintah tidak ditemukan
squid3: príkaz nenájdený
squid3: příkaz nenalezen
squid3: команда не найдена
squid3: командата не е открита
squid3: 命令找不到
squid3: コマンドが見つかりません