why should i use 16F876 MICROCONTROLLER

i would want to build an interface unit to an already existing electric to make it work like a prepaid meter
i have researched and i had 16F876 microcontroller
i don't know why i should use this microcontroller
please someone should give me the factors you should consider when choosing a microcontroller for this kind of project
please could some one give me an electric diagram for this kind of project
thank you

You can pretty much use any microcontroller that has sufficient memory, i/o pins, and oscillation speeds, along with other factors such as power consumption, etc.

honnestly i don't even understand the purpose nor the meaning of your project. For a beginner (i assume you are one), probably any micro controller will do just fine. the main thing you have to worry about is to chose a micro controller compatible with a programmer that is not too expensive and that is available around you. Exept that, well any general purpose micro controller will let you do virtually any simple project like the one you'r talking about (i guess it is simple but i am not sure coz i didn'tunderstand.. remember..? )

To make an existing electric meter "work like a prepaid meter" won't be easy. Probably not legal, either.