New to the game and I have a question

[Slick]

This is what you are thinking of:

7.2.9 Captured population (by any means) loses all of its racial attributes and is identical to yours except they retain their atmosphere breathing so can be used to populate your colonies appropriately AND they slowly get unhappy over time so you need to account for that so they don’t riot (riot police, upc, etc.).The positive happiness effect of 10 troops of any type will exactly cancel out the negative happiness of having alien population on a planet.

Not really the answer to the question at hand. The key (as stated by Gandalph) is that each troop adds 2 happiness points. You can read through the happiness.txt file to find values for all (or at least most) of the happiness modifiers.

Slick.