Why Metric prefixes step by factors of 1000: 1 GHz = 1,000 MHz. So to convert megahertz to gigahertz you divide by 1000, moving the decimal point three places left, and 2425 MHz becomes 2.425 GHz. This is the popular 2.4 GHz band used for Wi-Fi and amateur microwave work.
Watch out The choice showing 0.002425 GHz comes from dividing by a million instead of a thousand, which would be the kHz to GHz jump; 24.25 and 242.5 GHz move the decimal the wrong direction.
Going up a prefix (M to G), divide by 1000: the number gets smaller. 2425 MHz is the familiar 2.4 GHz band.