I am missing 3 imprtant nails on the bottom base. what to do

So yeah, the title explains it all. I was face timing a friend one day and I picked the computer up, I heard a snap as if I were snapping something back in, and the base was loose. I look closer, and three nails are missing. the middle, top left, and middle left. what screws do I need, where do I get them, what screwdriver do I need, and can I tighten them from the outside, or do I need to unhook the back. Thank you!!