Search notes:

C:\Program Files\Oracle\VirtualBox\UnattendedTemplates\win_nt6_unattended.xml

See also

The step Specify an unattended installation in Unattended OS installation with Powershell

C:\Program Files\Oracle\VirtualBox\UnattendedTemplates

The ‥autounattend.xml file found under C:\Users\username\VirtualBox VMs/<vmname>