Compared to our knowledge of 1AD, they would know only a very very small fraction. We can get a lot of information about the past because of the vast resources we have when compared to what was available in 1AD. We have a lot of writing, artwork and even archaeology available to us but to someone in 1AD looking at 2000BCE; although some, there was not as much writing or artwork that would give them a clear picture.

Herotodus is seen as the father if history and his book 'The Histories' is suspected to have been written within the 5th century. His introduction of the past world in Greece is based upon myth though showing a lack of knowledge of the past.

In Thucydides opening book in the History of the Peloponnesian War known as his archaeology he describes past Greece by looking at previous sources but once more touches upon myth as a background.

Past recorded history, such as Egyptian hieroglyphics, would be what was available to them but I guess they would only tell a story rather than be there as a historical writing.

To answer the question directly, compared to our knowledge I doubt they would have known much simply due to a lack of resources.