It's up to you how to go about it. You can install one of the apps & run that one command I linked to use that app as root, that will remove them all, but does risk doing other damage if you choose to delete the wrong thing.
Another option is to use Terminal to 'rm' the folder as root - but once again that is a risk. The OS tries to protect files & it appears you don't have permission to remove them, so it will require work to deal with that.
One more possibility, try resetting your home folder permissions. It may not help, but it might…
Backup before you begin – just in case.
Boot holding cmd+R. Recovery mode should startup (assuming you have a recovery partition).
Select Terminal from the Utilities menu.
Enter the word…
resetpassword
… & hit return.
The GUI app will open, select the main boot disk.
Select your user account in the popup menu.
Then click the Reset button at the bottom right. It will "Reset Home Folder Permissions & ACL's"
Repeat for the other users.
Quit ResetPassword from the menu,
Quit Terminal
Reboot
Try deleting the files again
The resetpassword tool seems to fail to fix permissions on occasion so the other options would be my first step. Whatever you decide it requires you to do some typing, it's not difficult you just need to take care. It's not clear on how we can help you, to gather more information we would need you to run commands which involves using Terminal…