If you want to find out the last time a Windows 11 PC was powered on, or shut down you can use the Event Viewer application.
Bring up Event Viewer by searching for it Windows. It will be preinstalled.
In Event Viewer, open the Windows Log menu and click on 'System'
Bring up 'Filter Current Log' from the Actions pane on the right. Enter '6005' in the Event ID field.
You can sort in the results by the date and time to find the latest time the PC was started.
Use 6006 as the Event ID to find when the PC was shut down.