[Sirtel]

Do you still have the serial number of the old Paperwhite? If yes, you can remove the DRM with the help of Calibre and the noDRM plugin. If you have no access to the serial number, then there's nothing you can do.

Edit: sorry, I forgot the books are presumably in the KFX format. If so, then you probably cannot remove the DRM from them. You should have downloaded and de-DRMed the books before you closed the old account.