You need to know the conversion factor between these two measures. The conversion unit is 1 Pound = 16 Ounces. Thus four pounds will equal 64 ounces.
One pound is 16 ounces, so four pounds is 64 ounces. Hope this helps.
One pound equals 16 ounces. You do the math.
There are some very good conversion web sites out there that may help in the future.