There are many methods for unlocking mobile phones, that is through software, codes,calculator,some tools , hardware and all ,but in that codes are best one, because it is easy to understand the instructions and enter into your mobile ,just give your IMEI number, country & network lock , then you can get the unlock code..........For the good place to get the unlock code for your Nokia 3100 model mobile phone, Just visit this site
Unlocking4free.com , It provides the step by step instructions and simple methods for unlocking mobile phones at a safe way...........