You can download the software from the internet. I am giving you the web link to download the software.
3230 Software
3230 Software
Where Can I Download The Nokia 3230 System Software For Free?
What do you mean by system software?? If you are talking about the Nokia pc suite, to install on the pc, then yes Zuhail gave you the right link. If you want to flash your phone, i.e. Install new software in it, then you can find it on the internet, its called a FIRMWARE. But updating it is a complex process, and I suggest you do it from an authorized nokia shop.
Security keypad lock software