The Deep Storage Safe is located in the back corner of the Command Center of the Deep Storage. It has a randomly generated code, meaning it is different for everyone in every Prey playthrough. However, where to find the code is the same every time.
The Deep Storage Safe Code is written on a sticky note that can be found on the back of Danielle's Workstation.
Prey (2017) Deep Storage Safe Code - GameRevolutionWATCH GALLERY