Help to retrieve values from web.config file urgent please

Question

Hi

I´m new in the c# business.
I need to store in a new text file, some values from a web.config file that has this tag

<add key="SqlConnectionString1" value="data source=Server\Instace;initial catalog=xpto;password=xpto;persist security info=True;user id=xpto;Enlist=True"/>



and i need to store at the value (data source=Server\Instace).

Can anyone help me please?