How do I know who many pixels my photo has?

What is the resolution (in pixels) of the images on a Disney Photo CD bought from the disneyphotopass website? I know it states 300dpi, but I'm after the resolution in pixels

• Answer:

  That is pixels. They are 300 dots per inch and also 300 pixels per inch. That equates to 300 pixels per screen inch. When you print on a dot matrix printer, it will literally print 300 dots. Most computer screens are 72 dpi. So a one inch 300 ppi (pixels per inch) image on a computer screen should look about 3 inches wide on the screen. It can be confusing, but once you get it... you get it.