Theory:

Unit prefixes are the symbols placed before the symbol of a unit to specify the order of magnitude of the quantity.
They are useful to express very large and very small quantities.
Example:
\(k\) (\(kilo\)) is the unit prefix in the unit, \(Kilometre\).
A unit prefix stands for a specific positive or negative power of 10. Some unit prefixes are given in the table.
 
Power of 10
Prefix
Symbol
1015
peta
P
1012
tera
T
109
giga
G
106
mega
M
103
kilo
k
102
hecto
h
101
deca
da
101
deci
d
102
centi
c
103
milli
m
106
micro
μ
109
nano
n
1012
pico
p
1015
femto
f
 
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Unit Prefixes