Here we have to convert m/s² into km/h²

1 km = 1000 m

1 m = 10^-3 km

1 hour = 60 min = 60 × 60 sec
or 1 sec =   h

Substituting the above values

3 m s^-2 = 3 × 10^-3 km ×   h^-2

= 38880 km-h^-2h

= 3.88 × 10⁴ km h^-2

dimension of energy  = $$\begin{gathered} {\mathrm{ML}}^2{\mathrm{T}}^{-2} \\ \mathrm{m}\Rightarrow \mathrm{M} \\ \mathrm{L}\to {\mathrm{ML}}^2{\mathrm{T}}^{-1} \\ \mathrm{G}\to {\mathrm{M}}^{-1}{\mathrm{L}}^3{\mathrm{T}}^{-2} \\ \mathrm{dimension} \mathrm{of} \left[\frac{{\mathrm{EL}}^2}{{\mathrm{M}}^5{\mathrm{G}}^2}\right] \\ \Rightarrow {\mathrm{M}}^0{\mathrm{L}}^0{\mathrm{T}}^0 \\ \mathrm{dimension} \mathrm{less} \mathrm{means} \mathrm{angle} \end{gathered}$$

Measurement is the process of attaching a numeric value to an aspect of a natural phenomenon. Measurement is making the quantitative knowledge of a physical quantity.