Windows is not showing on the screen and can't see it to drag it back into place.
1. Right click the icon on the taskbar and choose maximise, this will be a temporary solution
Minimise all windows
Right click on a blank bit of desktop and choose "Display Settings"
Click “Advanced display settings” at the bottom of the window.
Change the “Resolution” to another option, then choose “Apply“.
See if you can see the window on your screen now.
Change the resolution back to the previous value, then select “OK“.
Hold down the Shift key and right click the icon on the taskbar
Select the Move option
Use your arrow keys to move the windows back onto the screen.
If all is failing then you can cascade all your windows, again right click on the blank desktop, and choose Cascade Windows.