The metric unit of measurement for weight is ?

The metric unit of measurement for weight is a gram. The metric units for weight can be summarized by the word "KHDUDCM," which stands for "king henry died unusually drinking chocolate milk." If one where to take the first letters of the words, they would have all of the units for weight (knowing some prefixes and using the word gram at the end). K is for kilo so the first one is kilogram. H is for hecto which means that it is hectogram. D is for deka so that's dekagram. U is just the unit we are using. Since we are doing weight, this is the gram. The next ones are decigram, centigram, and milligram. That means that the metric units of weight are: kilogram, hectogram, decagram, decigram, centigram, and milligram.

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =