What is larger a megabyte or a kilobyte?

A megabyte is made up 1024 kilobytes. The next step up is gigabytes, the larger the file, the more kilobytes needed. It's the same as centimeters, then meters, then kilometers. It's just a unit of measurement for how much space if required (if designated for storage).

A small graphic may be a dozen kilobytes, a small picture with limited detail could be several hundred kilobytes, detailed pictures will start taking up increasingly more megabytes of space with the more detail they contain. A 3 minute song could be anywhere from 3 to 7 megabytes, etc etc.