How to unlock a restricted code on a LG phone... hi i just want to know how to be able to use a

Question

hi i just want to know how to be able to use a phone from another country with my sim card but i'm unable to use it because it says to put the restricton code and i don't know it. so i really need your help.the model is a LG phone and the model isG4015.i need an unlock code for my sons lg l343i phone. can any1 help pls?