I use Arduino Pro Mini. As I know, every MCU has a number. Different MCU has different number. How to get it ?
Could you be confusing the term micro-chip (often applied to any tiny, programmable electronic device) with the manufacturer named "Microchip" (who make the PIC series of micro-controllers, among many other products)? Microchip (the company) does make a line of products that have individually unique IDs. Most manufacturers do not provide unique IDs in their micro-controller devices, and AVR's Atmega 328 series devices do not have unique ID's.