**It appears he said it in _A History of the English - Speaking Peoples, Vol. 2 The New World_.**
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A short paper authored by Calvin George in 2009 quotes the book directly
> If the adventurers took books with them they took the Bible, Shakespeare, and later The Pilgrim’s Progress, and the Bible they mostly took was the Authorized Version of King James I. About ninety million complete copies are thought to have been published in the English language alone. **It has been translated into more than seven hundred sixty tongues.** The Authorized Version is still the most popular in England and the United States.
A snippet of the book is also available as a preview on Amazon.