N600 as a Wifi extender

> [...] i tried to connect it via the WPS but it didnt worked, [...]

   "tried" _how_?  What did you do, press the buttons and hope?

   What makes you think that a WNDR3400v3 can "work as a Wifi extender"?

   Visit http://netgear.com/support , put in your model number, and look
for Documentation.  Get the User Manual (at least).  Read.  Look for
"extend".

   If you can run an Ethernet cable (or equivalent) between the rwo
devices, then you should be able to configure the WNDR3400v3 as a
wireless acess point.  Look in its User Manual for "AP Mode".