How can I find partial pressure given moles?

Hint: Partial pressure is the notional pressure of that constituent gas if it alone occupied the entire volume of the original mixture at the same temperature?

Complete step by step answer:
The partial pressure of gas is a measure of thermodynamics activity of the gas’s molecules. Gases dissolve, diffuse and react according to their partial pressures and not according to their concentration in gas mixtures or liquids.
Dalton’s law expresses the fact that the total pressure of a mixture of gases is equal to the sum of the partial pressure of the individual gases in the mixture.
Ideally the ratio of partial pressure equals the ratio of the number of molecules. The mole fraction $xi$ of an individual gas component is an ideal gas mixture that can be expressed in terms of the component’s partial pressure or the moles of the component.
$xi = \dfrac{{pi}}{p} = \dfrac{{ni}}{n}$
And the partial pressure is an ideal gas of an individual gas component can be obtained using explanation.
$pi = xi.p$
Where: $xi = $ mole fraction of any individual gas component in a gas mixture.
$pi = $ partial pressure of any individual gas component can be obtained using expression.
$hg = $ moles of any individual gas component in a gas mixture.
$n = $ total moles of the gas mixture.
$p = $ Total pressure of the gas mixture.

Additional Information:
Henry’s law is a gas law that states that the amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid. The proportionality factor is also called Henry’s law constant. Atmospheric chemist after define the Henry solubility as,
${H^{cp}} = \dfrac{{{C_a}}}{P}$
${C_{ a}}$ is the concentration of species in the aqueous phase and $P$ is the partial pressure of that species in the gas phase under equilibrium conditions.
In underwater diving the physiological effect of individual component gases of breathing gases is a function of partial pressure. Using diving terms, partial pressure is calculated as.
Partial pressure $ = $ total absolute pressure $ \times $ volume fraction of gas component.

Note: The partial pressure of particularly oxygen and carbon dioxide are important parameters in tests of arterial blood gases. Oxygen toxicity involving convulsion becomes a problem when oxygen partial pressure is too high. The partial pressure of oxygen detrains the maximum operating depth of a gas mixture. The effect of a toxic contaminant such as carbon monoxide in breathing as is also related to the partial pressure when breathed. Carbon dioxide in the breathing loop of a diving retreater may become intolerable within seconds during descent when the partial pressure rapidly increases and could lead to panic of the diver.