How do I delete app residual files?

[MaGiCQQ]

Hi, I'm new to Truenas and just built my first ever nas last week.

After I deleted an app (Nextcloud), all the installed files were still in the drive. When I tried to delete the residual files, it said I need permission to do so.

I have granted my user all the dataset permissions.

Please help. Thanks.

 

[MaGiCQQ]

After doing some searches, I figured out how to delete folders using shell commands.