From Mechanics

First convert to SI units. In this case grams are converted to kilograms which is the standard unit for mass.

\displaystyle 4\ \text{grams}=0\textrm{.}004\ \text{kg}

\displaystyle W=mg=0\textrm{.}004\times 9\textrm{.}8=0\textrm{.}0392\ \text{N}