$${E = \frac{U}{d} = \frac{3 \cdot 10^4\, \mathrm{V}}{0,12\, \mathrm{m}} = 2,5 \cdot 10^5\, \mathrm{\frac{V}{m}} = \underline{\underline{2,5 \cdot 10^5\, \mathrm{\frac{N}{C}}}}}$$