The quantity of matter contained in a body is called the mass of a body.
The SI unit of mass is kilogram (kg).
We can measure the mass of a body by using beam balance or pan balance.
The three units of mass in measurement are kilogram, gram and pounds.

The 6 kg mass of a body means that a body is 6 times heavier than the mass of 1 standard kg.

The 5 kg mass of a body means a body is 5 times heavier than the mass of 1 standard kg.

2 kg

\begin{align*} \text {Converting into grams} \\ &= 2\: kg \\ &= 2\times 1000\: gm \\ &= 2000 \: gm \\ \end{align*}

5.5 kg

\begin{align*} \text {Converting into grams} \\ &= 5.5\: kg \\ &= 5.5\times 1000\: gm \\ &= 5500 \: gm \\ \end{align*}

2 kg

\begin{align*} \text {Converting into grams} \\ &= 2\: kg \\ &= 2\times 1000\: gm \\ &= 2000 \: gm \\ \text {Converting into milligrams} \\ &= 2000gm \times 1000\: gm \\ &= 2000000 mg\end{align*}