Depends how its written. In your example, the answer would be there are no zeros after the 3. ;-)

Also depends which version of "billion" you're using, it could be either: 1,000,000,000 (short version) or 1,000,000,000,000 (long version).

http://en.wikipedia.org/wiki/Billion

edit: add link & proper version titles.

In dollars, its almost universally assumed billion is "short billion". (Although, occasionally you still hear people saying it)

It would be a fabulous retort if you were this fellow and you actually did happen to know. "Short or long" would be almost as good a come-back as "African or European" when asked about unladen swallows.