We have the wavelength - from this we can find the momentum by using the DeBroglie equation

l_dB= h/p

so p = h/l

= 6.63 x 10^-34/1.2 x 10^-10

= 5.5 x 10^-24 Ns

and p = root of (2meV)

so p²/(2me) = V

= (5.5 x 10^-24 )² / (2 x 9.1 x 10^-31 x 1.6 x 10^-19)

= 105V Ans