Explanation of SI prefixes as defined here: http://physics.nist.gov/cuu/Units/prefixes.html.

10^1  = deka (da) = 10
10^2 = hecto (h)  = 100
10^3 = kilo (k)      = 1000

Basically 10^x means x zeros after the 1,
so 10^9 (Giga) = 1 000 000 000

easy enough?

most commonly used are multiples of three, so get used to using
10^3 - k - kilo
10^6 - M - mega
10^9 - G - giga
10^12 - T - terra

e.g
375,000,000,000  IOTA would then be 375 G-IOTA
567,890,000 IOTA would be 567.89 M-IOTA

please everyone use those prefixes from now.