hi, just to add on examples..
moles = (no. of particles)/ NA where NA is avogadro's constant
how many ions in 0.500mol of NaCl(aq)
no of ions = 0.500 x NA x 2
how many moles of CO2 is 3.01 x 1023 of CO2
moles = 3.01 x 10^23 / NA
so you can use to find moles or no.of particles.