Answer
About 926 feet of shelf space.
Work Step by Step
divide 5 billion by $5,$ to get the total number of words.
$5,000,000,000 / 5=1,000,000,000$ words.
Then divide this by $300,$ to get the number of pages.
$1,000,000,000 / 300 \approx 3,333,333$ pages.
And finally, divide that by 300 to get the length of shelf space.
$3,333,333 / 300=11,111.11$ inches which is about 926 feet.