There are 1,000 kilobytes in one megabyte of data. The prefix kilo- means 1,000, while the prefix mega- means 1 million. To convert one megabyte to kilobytes, multiply one by 1,000 to obtain the answer of 1,000 kilobytes.
A byte is a quantifiable amount of data. For example, a typical email uses one to two kilobytes of data. There is about one byte of data per stored letter or other one-page text document. On a larger scale, an MP3 file that plays for a few minutes takes up a few megabytes; one minute of MP3 audio takes up about one megabyte of data.