Two definitions meet here. Density is mass per volume, $\rho = \dfrac{m}{V}$ — $\rho$ is the Greek letter rho, said “row”, and for a gas it is usually quoted in grams per litre. Molar mass is mass per mole, $M = \dfrac{m}{n}$, in grams per mole. Put $n = \dfrac{m}{M}$ into $PV = nRT$, divide through by $V$, and the mass turns into a density on its own:

$\rho = \dfrac{PM}{RT}$ — read aloud rho equals P M over R T. Four letters, four jobs: $\rho$ is the gas's density in g/L, $P$ its absolute pressure in kPa, $M$ its molar mass in g/mol, and $T$ the absolute temperature in kelvin, with $R = 8.314\ \mathrm{kPa \cdot L/(mol \cdot K)}$ refereeing as always. Solved the other way, $M = \dfrac{\rho R T}{P}$, it becomes the classic identification: weigh a known volume of an unknown gas, and its molar mass — and usually its name — falls out.

Two sanity rails worth carrying. Heavy molecules make dense gases at the same conditions, because $\rho$ is directly proportional to $M$. And hot gas is thin gas: $T$ sits underneath, which is the entire operating principle of a hot-air balloon. If your answer says otherwise, something upstream is inverted.