Their onboard LEDs are connected to pin D13, and their serial RX/TX pins are on pins D0 and D1, respectively. Additionally, the Nano and Micro feature 20 digital pins, labeled as RX, TX, D2 to D13 ...

Because of the Nano's small form factor, it doesn't have much space to accommodate a jack. There are, however, still three other ways you can power your Nano: via the USB port, VIN pin, and 5V pin.