The quickest way to get the total NY 529 contributions from 1998 to 2017, would be to contact the plan administrator who manages the 529 plan. The contact information for the plan administrator should be on your 529 plan statement.
The NY 529 plan online account page only allows you to see contribution information back to 2003, and you have to select each year and add up the contributions.
[Edited 1.27.18 | 3:05 PM]
