where will i find the network security code on my rooter?
You can't that's the whole point. If somebody installed it and put a code in it, you will now be paying them to recover it. If you installed it follow the manufacturers directions to reset it and put a new code in it. You may need to contact the manufacturers tech support. Next time remember to write down all the codes. Never allow someone to install hardware without giving you all the codes, otherwise you have to call them and pay them to recover codes, it's a scam quite popular with installers. Don't fall for it.