I PLACED MY SIM CARD INTO ANOTHER PHONE AND IT

the PIN that is being asked by you is the securtiy 4 digit no that you might have set for your sim card. The default PIN is 1234 or as set by your network provider. If you do not know your PIN then you can call your customer care unit of your network provider and ask them for it. If you have forgoten it, then also you have to call them and ask them to reset it.

Hope you this will resolve your problem.

Do reply back if you need more help.