If for example my nokia 3200 has a security code if i change the sim card, and i forgot it, how can i get it?

i mean i would like to change my sim on my phone but i forgot the security code, how do i change it now?If for example my nokia 3200 has a security code if i change the sim card, and i forgot it, how can i get it?
The Default Security Code for Nokia phones is 12345