What is the size of the observable universe in feet?
Its not really meaningful to express the size of the universe in feet. But its 93 billion light years in size (Wiki).
This means that if you fired a laser beam from the edge of the known universe towards the other side, it would take 93 billion years for the light to travel this distance.
Expressing the size of the universe in feet is not meaningful as feet are a more useful unit when measuring things about the size of a house or a city block. Other units are more appropriate for larger objects - say, the distance between cities or towns - miles or kilometres are more appropriate. Light years are the most appropriate for measuring really big objects - like the universe!