Google failed me.

How do I dial a number with an extension?

Do I just dial

Number with #extension after it?

It's not one of those automated ones that says "please enter the extension number"
just enter it when you call the number? that usually works for me
"We are not concerned with motive, with higher ethics. We are concerned only with cutting down crime-."
take original number. Take extension. count number of numbers in extension, most likely 4. Take 4 numbers away from original and replace them with the extension numbers. Et voila!