There is no exact date or history that tells when was gambling used but since money laundering was done dated back from as early as 2000 BCE[2], It is possible that gambling is used to launder money somewhere along that time frame.
It's not clear to me where that information in the article comes from, but I'm pretty sure that money didn't exist in 2000 BC. It was not even invented until around 900 BC, when it started being used in China. I think they meant to say that money laundering has existed for 2000 years, not that it existed in 2000 BC.