Help... anyone!!!

At work we have been asked to use higher DPI settings for taking photos for our school magazine.

Most of the cameras are around 70/75 DPI.

Is there a way of changing the settings as I think the DPI needs to be at least 150 for uploading to the photo mag comany. Most people are really confused and are thinking that all of the photos we have been taking all year have been useless.

Any links, ideas, suggestions, advice will be greatly appreciated.