Hi, Im actually a newbie to Arduino. But because of a misunderstanding , I thought its micro USB on NANO and with that assumption I bought around 20 Arduino NANO. But on getting those in hand I found its not having a Micro USB power supply (I thought I just need mobile charger to power it) and its having a Mini-B usb power which I dont have. Is there is any alternative way if I have a 12v or or 5v power supply? Or is it only work with Mini-B USB type connector to power it up?
You can power it through the Vin pin or the 5V pin with the 5V. The more important question is "How do you plan to upload sketches"?
Buy a mini usb cable. it costs you only the price of 1 arduino nano... or get a micro usb to mini usb adapter.
Just for testing and simple projects you can use 7 to 12v supply to power using the VIN pin and GND pin.
Update: Tip- Before placing any bulk order just make sure to buy one as a sample to see if it works according to how you wanted it to. 
tinman13kup:
You can power it through the Vin pin or the 5V pin with the 5V. The more important question is "How do you plan to upload sketches"?
Thanks a lot for that information. I thought its 5v out
sforsandeep:
I thought its 5v out
It can also be used as a 5V out.