If you mean the "Metric" system (SI), there are a great many prefixes, including kilo- (thousands), hecto- (hundreds), milli- (thousandth), micro- (millionth), pico- (trillionth). Hect(o)- is not used much in scientific work with the exception of hectoPascals (hPa) which replaced millibars in meteorology and occasionally in the unit of area hectares.
Centi- is the SI prefix for 0.01.
The SI prefix meaning of 0.001 is "milli-". This prefix denotes a factor of 1/1000, so 0.001 can be written as 1 milliunit.
The SI prefix for million is "Mega".
No, "femo" is not a SI prefix. The SI (International System of Units) prefixes are used to denote multiples or fractions of base units in the metric system, such as kilo-, mega-, milli-, etc.
There is no prefix at all, its just leave as is.
There is no prefix for "10-3".
There is no special SI prefix for the number 3.
The prefix is milli, abbreviated "m".
Micro
The SI prefix deci- means one-tenth (1/10) or 0.1. It is used to denote a factor of 10^-1 in the International System of Units.
nan0-
Actually, "si" is not a recognized prefix for a factor of 0.01. The prefix "centi-" is commonly used to represent a factor of 0.01 in the metric system.