Command "upgrade" is not defined! Problem

I always gets this error. I wanted to migrate from OwnCloud to NextCloud.

Here the code:

root@BANANAS ~www/nextcloud # sudo -u www-data php occ upgrade

Nextcloud is not installed - only a limited number of commands are available

Command “upgrade” is not defined.

Who can help me fast? I need my calender.

Please check if you installed all required modules:

The ownCloud setup is running on your machine (then normally the php config should be quite ok)? Between which version are you updating?