I have two memory cards for my camera and one card is 16MB and the other is 64MB
My question is which one holds more pictures the 16MB or the 64MB ?

What Model do you have?
Different Cameras and Devices have a max they can handle. Last SD card I heard of, I believe was 32 Gig or 64 Gig.

Of course the bigger card (64mb) will hold more than the smaller 16mb card using the SAME file size. (unusual exception is you could actually get more shots on the 16mb card if you set the camera for small file size/low quality/higher jpg compression and then changed to max quality/size or RAW if you have a DSLR before you put the 64mb card in the camera and then you would get a smaller number of shots on the 64mb card but remember that it depends on the file qualilty/size settings you choose). Hope that helps.