The safe in the Ballistics Lab has a randomly generated safe code, meaning it is different every time for every Prey playthrough. That being said, the place you find the safe code is always the same.
You can find this safe code under a floor grate in the corner of the Ballistics Lab. You'll need Leverage 1 at least to be able to remove this grate. Then, simply pick up the materials, and you'll see the safe code.
That's it! Enjoy your loot.
Prey (2017) Ballistics Lab Safe Code - GameRevolutionWATCH GALLERY