HP ZBook Studio 15-G3 15" i7, 256GB SSD Workstation

What kind (size) drive is in this? I’ve seen videos showing swapping out a standard 2.5" laptop battery, and videos showing the M.2 drives.

I’ve got a standard 1gb SSD I want to put in this. If I can’t use it and I need to replace it with the M.2 drive, that jacks up the price a good $300 for me.