how many pics can be held on a 16MB memory card?

Unless this is a typo & you meant 16GB, not many. My camera @ high rez won't fit one picture on it, and most point & shoot cameras will give you 3-10 pictures.

If it is a 16GB card, most current & older point & shoot cameras can't even utilize it (many still have problems with anything over 4GB),

The average point & shoot will take a 2-4MB file (so divide that into 16 (MB) or 16000 (GB) for a rough idea on number of shots).

The average SLR makes 3-6MB jpeg files and 10-24MB RAW files (same math as above).

Of course, as long as your camera can handle the card, when you insert the card, the LCD will tell you how many pictures are left at your current resolution.

There is no one answer to this...you must state at what resolution you are shooting...the higher the resolution, the fewer the pics. Are you shooting JPEG or RAW? If, like most people, you are shooting JPEG at medium resolution, you will not fill that card in 10 years!