The answer is 8.13 x 10²⁸ atoms.
First we calculate the number of moles using the molar mass.
molar mass of helium = 4 g/mol.
it means that 1 mole of helium atoms weighs 4 gram.
Now we have 540 kg of helium =540000 grams
Number of moles in 540000 grams;
540000 / 4 =135000 mol
Now in one mole there is 6.02 x 10²³ atoms
So, in 135000 mol there is;
135000 x 6.02 x 10²³ = 8.13 x 10²⁸atoms