The formula units of NaNO3 that are in 2.99 moles of NaNO3 is
1.80 x 10^24 formula units
calculation
Use the Avogadro's constant to calculate the formula units
that is, 1 mole = 6.02 x10^23 formula units
2.99 moles =? formula units
by cross multiplication
= (2.99 moles x 6.02 x10^23 formula units) / 1 mole = 1.80 x 10^24 formula units