Hi pqraby, is that the password to the wireless network? You can retrieve it by accessing the setup page of the router. The default IP address of the router is 192.168.1.1. Just leave the Username field blank and type "admin " as the password. Click on the Wireless tab then Wireless Security sub-tab. Look for the Passphrase or WPA key.
You may also check this link, http://kb.linksys.com/Linksys/ukp.aspx?vw=1&docid=476326f36c294e579ba6691a8db5411e_3698.xml&pid=80&respid=0&snid=4&dispid=0&cpage=search
Hope that helps.