The momentum \( p \) of an object is calculated using the formula:
\[ p = m \cdot v \]
where \( m \) is the mass of the object and \( v \) is its velocity.
For a 2 kg body moving with a speed of 3 m/s:
\[ p = 2 , \text{kg} \cdot 3 , \text{m/s} = 6 , \text{kg m/s} \]
Therefore, the magnitude of the momentum is 6.0 kg m/s.