1. biodelta
How many atoms of Helium in a volume of : 4.25 x 10 ^ - 9 cubic 25 deg celcius?
I’ve had a look at the question as you write it. I get the impression that there are things missing from it ...
Ideal gas equation.
The pressure is P
V is the volume in cubic metres
n is the number of moles
R is the universal gas constant, 8.31.
T is the absolute temperature in kelvins. Add 273 to the temperature in Celsius.
NA is Avogadro’s number
Ideal gas equation.
This is a combination of Boyle’s law and Charles’ law.

2. biodelta
How many atoms of Helium in a volume of : 4.25 x 10 ^ - 9 cubic 25 deg celcius?
Standard Temperature and Pressure (STP) ?
So the question doesn’t fall into any of these categories.