How many pictures would a digital camera store if it had 32 mb of internal memory?

It depends on how many megapixels the camera has, which determines the size of the photo.
But I can tell you that 32 MB is a tiny size and is quite useless. Some cameras might only be able to store 10-20 photos with that.

So, you would need to buy a memory card (512 MB minimum). This will allow perhaps 150-250 photos (depending on which camera you are using).