Everywhere! xD
Well the 3 main Nadis being the Shusumna, the ida and the pingala, they are the biggest and go through all the 7 main chakras.
The Shushumna goes straight, and the ida and pingala wave from each chakra out and in again. And form at the 6th in the brain a heart shape.
You have 144000 Nadis tho ( if I remember correctly)