A level physics nuclear question

Radioisotope thermoelectric generators (RTGs) are electrical generators powered by radioactive decay. As a radioisotope decays some of the energy released is converted into electricity by means of devices called thermocouples. In this way RTGs have been used as power sources in satellites, space probes and heart pacemakers.
The Cassini space probe was launched in 1997. It carried three RTGs each containing 11 kg of a nuclear fuel, plutonium oxide (a compound having two oxygen atoms combined with every plutonium-238 atom). In 1997, when the probe was launched, the power released from one gram of plutonium oxide was 500 mW.
Plutonium-238 is an alpha emitter, decaying into uranium(U). The half-life of the decay is 87.7 years.
mass of one mol of plutonium-238 = 238 g
mass of one mol of oxygen atoms = 16 g

Q) Calculate the number of plutonium-238 atoms in the total mass of the plutonium oxide in the Cassini probe at the beginning of its mission.

Can someone please explain how to solve this one, I honestly have no idea where to start?

This part of the question deals with the mole concept(s) that you learn in chemistry @ GCSE or Ideal Gas topics in physics @ A level.

Some guiding steps:
1. Find the molar mass of plutonium oxide using the following info from the question:
plutonium oxide: a compound having two oxygen atoms combined with every plutonium-238 atom)
mass of one mol of plutonium-238 = 238 g
mass of one mol of oxygen atoms = 16 g

2. Find the amount of plutonium oxide in moles in the Cassini probe.

3. Using Avogadro’s constant to determine the number of plutonium-238 atoms.

The following webpage has all the equations that you need.
https://edu.rsc.org/infographics/calculating-moles-and-using-avogadros-number/4015494.article