How many atoms are present in 52 u He?

$He$ has an atomic mass of 4u, and each mole of $\mathit{He}$ has a mass of 4u. There are $52\mathit{ moles}$  in one unit of $He$,

So $52/4=13\mathit{ moles}.$
$1\mathit{ mole}=6.022\times 10^{23}$ atoms
in 13 moles, the number of atoms$=13\times 6.022\times 10^{23}$
$\Rightarrow 78.286\times 10^{23}\mathit{ atoms}$
$\Rightarrow 7.8286\times 10^{24}\mathit{ atoms}$
There are $7.8286\times 10^{24}$ atoms in $52\mathit{ u}$ of $\mathit{He}$.
In $52\mathit{ u}$ of $\mathit{He}$ $7.8286\times 10^{24}$ atoms are present.

There are $7.8286\times 10^{24}$ atoms are present in 52 u of He.