For which Generation? ? As far as I can tell they're in every generation.
If you're referring to the .rar, well they'll in the save, so no need to double submit...
For Gen 3/4 you can learn how to edit the files so that PID/IV combo matches. (those data were generated together, and we know how they're generated)
Guide:
Else, in Gen 7, just perform Hyper Training to max out their IVs.
To Hyper Train, their Level must be 100. Then hold Shift on your Keyboard and click on the IV stat.
The stat will turn green (example in image below). You cannot Hyper Train a stat that is already 31 IV.
In-game, the Pokémon will look and act as though the Hyper Trained stat is 31 IV.
However, when breeding, it'll pass down the standard stat. (Which doesn't matter, since it's an Unown)