How many grams are in 2000 mg?

$1$ $m g$ $=$ ${10}^{-} 3 g$.
$2000$ $m g$ $=$ $2000 \cdot \cancel{m g} \times {10}^{-} 3 \cdot g \cdot \cancel{m {g}^{-} 1}$
$=$ $2.000 \cdot g$