Hi Niraa,
Welcome to the Forum.
I assume you have a download version of SSE from www.shipsim.com . If so go to the website and log in. Once logged on the 'Account Management' page will open. In that page, you will find 'Orders and Downloads'. Click on this and under "Downloads Overview" you should see Ship Simulator Extremes. Click on this and you will be presented with a window which prompts you to save the file. Save it where you want. This will be a .exe file which you can use to re-install SSE again. The License Key will also been shown under "License Key Overview".
Hope this helps.
Regards
vin_sun