1. 1.204 x 1024 atoms He = ? moles He

Check your chemistry textbook (or class notes) concerning molar mass, then look up the value for oxygen.

Then divide Avogadro's number into the given amount of atoms, to find the number of moles.

Then combine this result appropriately with the molar mass, and voilà!

... Then reconsider posting homework questions without showing the work you have already done.