Why Kilo means thousand and mega means million, so 1 MHz equals 1,000 kHz. Multiplying 3.525 by 1,000 shifts the decimal point three places right, giving 3525 kHz (which is also 3,525,000 Hz). This is a common ham frequency in the 80 meter band.
Watch out The choice of 3,525,000 is the value in hertz, not kilohertz; that would only be right if the unit were Hz. Dividing instead of multiplying gives the tiny 0.003525 figure.
MHz to kHz: move the decimal three places RIGHT (x1000). Going to a smaller unit always makes the number bigger.