This first example uses "Female Power Supply Adapter with Screw Terminals" that plug right into the Power Supply on one end and allow the Nano wires to be screwed into the other.
The next example uses a "Multi-Power Adapter" and also "Female Power Supply Adapter with Screw Terminals". The "Multi-Power Adapters" are available in 2, 4, and 8 versions.
The final example shows how you can cut off the adapter from the end of the power supply cable and then use wire nuts to directly connect the bare wires on the Nano's.
You can extend the length of wire on the Nano's by using "22 Gauge Wire"