Yes, you need 6/2= 3 times as many mols of acid as of aluminum. Since you have 1.45 mols of aluminum, you will need 3(1.44)= 4.35 mols of acid. Now by "2.40M acid", I presume you mean one mol of acid per liter (it's been a while since I took chemistry!) so you would need liters of acid. That is volume, not number of mols.