According to the question, The number of sodium atoms in 1 molecule of sodium ferrocyanide, ${\mathrm{Na}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$ is $4$

The number of sodium atoms in $1$ Moles of sodium ferrocyanide,

${\mathrm{Na}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$ is $4$ Times Avogadro number. It is equal to $4x6.023x{10}^{23}$.

The number of sodium atoms in $0.5$ Moles of sodium ferrocyanide,

${\mathrm{Na}}_4\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6\right]$ is $2$ Times Avogadro number. It is equal to $2x6.023x{10}^{23}$or $12x{10}^{23}$.