The first thing to do is rewrite the number of #Ni# atoms in a form that can make the calculations easier. Use scientific notation to help with that

#6,000,000,000 = 6.0 * 10^(9)# - six followed by nine zeros.

Next, focus on how many atoms you would get if you had exactly one mole of #Ni#. As you know, one mole of #Ni# has #6.022 * 10^(23)# atoms of #Ni#.

If you compared these two numbers, #6.0 * 10^(9)# and #6.022 * 10^(23)#, it'll be obvious that you have *less* than 1 mole.

#6.0 * 10^(9)" atoms of Ni" * ("1 mole of Ni")/(6.022 * 10^(23)"atoms of Ni") ~= 1.0 * 10^(-14)" moles of Ni"#

In other words, #1/10^(14)"th"# of #"1 mole of Ni"# contains #6.0 * 10^(9)# atoms of Ni.