What are you trying to find?
The specific heat capacity of sand is much less than water because of which sands require less energy to cool down and similarly less energy to be heated... because of this it feels like sands absrob heat faster than water
To convert from moles to atoms you times the number of mols by Avogadro's number (6.022×10²³)
0.74 × 6.022×10²³ = 4.45628×10²³