How to get 300ppi resolution?

I'm getting photos from someone and when she gives them to me, they are 72ppi. This is for desktop publishing, so I need to have 300ppi. Is it a setting in the camera? Or some type of output? They are.jpeg should they be.tif? Her camera is either a Nikon d300 or d60 and she uses a Mac.

Added (1). Ppi meaning pixels per inch

Might be the setting she's choosing to convert them to jpeg. I took a picture earlier today with a Nikon D3000 in RAW and saved it as a JPEG in Photoshop. The DPI was 240 at a setting of 12.

You are confusing display resolution with print resolution. Your monitor is telling you 72dpi, when you send the work to print, you tell the printer 300dpi, and leave it be. The file is all you need, don't worry about dpi vs ppi.