Answer
$250\ cm^3$
$0.250\ L$
$0.250\times10^{-3}\ m^3 $
$0.250\ dm^3$
Work Step by Step
We use stoichiometry, making sure that all units cancel out to $cm^3, L, m^3, \text{and} \space dm^3$, respectively, to obtain:
$250\ mL \times
\begin{cases}
1\ cm^3/mL=250\ cm^3 \\
1\ L/1000\ mL = 0.250\ L \\
1\ m^3/10^6\ mL = 0.250\times10^{-3}\ m^3 \\
1\ dm^3/1000\ mL = 0.250\ dm^3
\end{cases}$
