i think you have two possibilities:
Update 8.0.2 to the latest 8.0 version, afterwards to the latest 8.1 version, then to the latest 8.2 version and finally to 10.0.10
From what i know there is no “migration” of data available from and older version to a newer one without losing the users and the shares they have created. If you’re o.K. with this you could try to re-create all users in your new 10.0.10 installation, then move over the data from the old 8.0.2 installation to the new one and finally run the occ files:scan command to update the ownCloud internal database with the information about the new files.
Not sure how sync-client will behave with this approach, they might see the “new” installation wrongly and could start to delete their local files.