What pin to power arduino nano from power supply

I want to power the arduino nano from an external power supply of 13.8 volts.

The docs here say pin 30 - https://www.arduino.cc/en/Main/ArduinoBoardNano

But, I read somewhere else it was the vin pin (the one beside the ground.)

Anyone know for sure?

Vin pin can be used to power the boards. The 5V regulator will get pretty hot powering from that high a voltage.

Vin is pin 30, by my count.

Start at Tx as 1, D12 is then 15, D13 is 16, Vin is 30.

(via the 5V pin which the page says is 27 and Vin is 3 along.)

You would be exceeding the recommended max voltage with 13.8V, and others on the forum recently have had problems such as burning out the onboard regulator when exceeding 12V. Various Nanos may have different regulators depending on the manufacturer and version, so you would have look at what regulator is on your Nano, and look in the data sheet for that regulator to research. It would be a better idea to get a small DC-DC buck converter, and adjust it for 5V and power the Nano via the 5V or VCC pin.