Hi! From what I have gathered, you won’t be able to skip any major versions. So this means that you’ll g from 9.0.9 to 9.1.6 (released yesterday May 30) and then to 10.
If you want to upgrade from 9.0.9 to 9.1.6 you need to update your repositories.
For 9.1 they are here: https://download.owncloud.org/download/repositories/9.1/owncloud/