how to copy file from my ubuntu desktop to windows desktop using open terminal

Hi.

You can use a combination of PuTTY for SSH and WinSCP for file transfer (basically scp for windows). Here's a link to a guide on how to install the softwares:

http://ged.msu.edu/angus/tutorials/using-putty-on-windows.html

my server is core edition and i need to perform this copy without installing any app on my core server only using my admin password

You can run WinSCP on core edition as well with no GUI. However, as far as I know there is no way to do it without installing any kind of software.

Thanks for accepting. Let me know should you require anything further.