Norco contains a combination of acetaminophen and hydrocodone.
It takes about 2 to 4 days to get hydrocodone out of your system, and 1 to 2 days for the acetaminophen.
The rate at which a drug is eliminated from your system is related to its half life.
Hydrocodone has a half life of around 4 hours and acetaminophen has a half life of around 2 to 3 hours. It usually takes about 5 to 6 half lives for a drug to be eliminated from your system.

Many factors influence how long a drug remains in your system. Body metabolism, physical condition, state of hydration, age, frequency and method of usage will all affect your result.

It is the hydrocodone component that is of interest when urine drug testing.
If you know you are going to have a drug test the best thing you can do is stop taking the drug.

https://www.drugs.com/norco.html