If I have #"Avogadro's number"# of #H_2# molecules, I have #2xx"Avogadro's number"# of hydrogen atoms; if I have #"Avogadro's number"# of pairs of boots, I have enough boots to shoe #"Avogadro's number"# of people (I'll probably have the wrong sizes tho). If you specify #"Avogadro's number"#, you specify a given numerical quantity.
To continue, if I have #"Avogadro's number"# of #CH_4# molecules, then how many atoms do I have? And what is the mass of these atoms?