Answer:
 12 moles Pb(NO₄)₂ needed. 
Step-by-step explanation:
 3Pb(NO₃)₂ +2AlCl₃ => 3PbCl₂ + 2Al(NO₃)₃
Given => ? moles 8 moles
from reaction stoichiometry, 2 moles AlCl₃ requires 3 moles Pb(NO₄)₂ then 8 moles AlCl₃ requires 3/2(8) moles of the Pb(NO₄)₂ => 12 moles Pb(NO₄)₂ needed.