Answer
$3.25\times10^{3}\,m/s$
Work Step by Step
Recall that de Broglie wavelength is $\lambda=\frac{h}{mv}$ where $h$ is the Planck's constant, $m$ is the mass and $v$ is the velocity.
$\implies v =\frac{h}{m\lambda}= \frac{6.626\times10^{-34}\,J\cdot s}{(1.6726\times10^{-27}\,kg)(122\times10^{-12}\,m)}$
$=3.25\times10^{3}\,m/s$
