How to convert Chemistry

I'm taking Chemistry 1 Honors and.... please help me learn some methods of coverting these kinds of meters?

Megameters
Kilometers
Grams
Liters
Meters
Seconds
Decimeters
Centimeters
ml (milliliters?)
Micrometers
Nanometers
Picometers

Ex: 5 Mm to km.
5680 mg to nanograms.

Please help me. There's a test on Monday, next week, and really want to bring my grade up, not letting it fall.

Divide 1000 for which meter? I'm trying to get the "fractions and different kinds of meters" lesson absorbed into my mind. I'm confused on what to convert the science units to.... Thanks!

There are 16 SI prefixes but you will probably only need to memorize 12-
T tera 10^12
G giga 10^-9
M mega 10^6
k kilo 10^3 example kilogram = 1 gram x10^3 (1000 g)
h hecto 10^2
da deka 10^1
d deci 10^-1
c centi 10^-2 example decimeter = 1 meter x 10^-2 (0.01 meter)
m milli 10^-3
u micro 10^-6
n nano 10^-9
p pico 10^-12

5680 mg to ? ng
Which is bigger mg or g? grams
How many mg in 1 g? 10^3
Which is bigger ng or g? grams
How many nanograms in 1 g? 10^9
5680 x 10^9/10^3 = 5680x10^6 or 5.680x10^9

5 Mm to ? km
Which is bigger Mm or m? Mm
How many meters in 1 Mm? 10^6
Which is bigger km or m? km
How many meters in 1 km? 10^3
5 Mm x 10^6/10^3 = 5x10^3 km

put the item you are leaving in the denominator and the item you want to get to in the numerator. You will have to memorize the factors