The Sailor Stars in the Sailor Moon manga are not transgender. The manga portrays their genders consistently without any indication of them being transgender.
Sure, the Sailor Moon manga is finished. It wrapped up nicely, giving closure to all the characters and their adventures. But you can still enjoy re-reading it or exploring related merchandise and media.
The number of Sailor Moon manga varies. There are the main series, along with special editions and adaptations. But as of now, I'd say there are at least a dozen or so.