You will most likely have to enable the new apps system and choose a pool again. You can choose the same pool you used for kubernetes based apps backend.
The new apps backend stores the data in a hidden dataset called .ix-apps which can be accessed from shell under /mnt/.ix-apps
But i suggest you switch to using hostpaths and not iXVolume which makes it easier to backup apps datasets via snapshots or reinstalling apps since you only have to point the new install to the old dataset.