Error Deleting Dataset ./jails/syncthing_2

[mrteaiot]

I am not able to delete my syncthing_1 and syncthing_2 dataset on the jails. I create this before I upgrade to new version of FreeNAS. I install the syncthing twice but never successfully use them and forgot to delete them before upgrade. I did not see any plugin installed and not service running. After upgrade the FreeNAS, I plan to delete this unused dataset or folders before reinstall syncthing on the new UI. I did not see it on the Jails UI but I can see these dataset on the Storage/pools/jails UI. But not able to delete the dataset due to this error:
Error deleting dataset <i>RAIDZ-40TB/jails/syncthing_1</i>.
[EFAULT] Failed to delete dataset: cannot unmount '/mnt/RAIDZ-40TB/jails/syncthing_1': Device busy

and after try promote dataset and delete them I got this message:

Error deleting dataset <i>RAIDZ-40TB/jails/syncthing_2</i>.
[EFAULT] Failed to delete dataset: cannot destroy 'RAIDZ-40TB/jails/syncthing_2': filesystem has dependent clones use '-R' to destroy the following datasets: RAIDZ-40TB/jails/syncthing_1 RAIDZ-40TB/jails/.warden-template-pluginjail-11.0-x64-20190324182441

Please anyone can help appreciate it before I create new syncthing on the new UI.