1) If there are 8.800x10^25 atoms of tin, how many moles is
this, and what would be the mass?

ii) You have a sample containing 2.575x10^24 molecules of
water. How many moles is this, and what is its mass?
Please help me I have no idea how to do this

Avogadro’s number (6.022x10^23) is the number of atoms in a mole of any substance.

8.800x10^25 / 6.022x10^23 = 146.13 mols in tin

Mass = moles x Ar(Sn) = 146.13 x 50 = 7306.5g

You can apply this to the other question.

2.575x10^24 / 6.022x10^23 = 4.276

Mass = moles x Mr(H20) = 4.276 x 18 = 76.968g

Hope this helps.