Airport Extreme(s) and Airport Express(s) Network

but i need to connect three airport express to the 6th generation airport extreme and its not working with the wire network its only connected by wireless.

The 3 AirPort Express devices will all need to be reset back to factory default settings before they can be reconfigured to connect using Ethernet.

on the airport express should be connected on the WAN or on the LAN

WAN on the AirPort Express to LAN on the AirPort Extreme.

or what i need to modified on the settings?.

As mentioned above, each AirPort Express first needs to be reset back to factory defaults

Then, connect the Ethernet from the WAN on an AirPort Express to the LAN on the AirPort Extreme

Use the setup "wizard" to automatically configure the AirPort Express to "extend using Ethernet"

Once that is done, configure the other two AirPort Express devices the same way.

Post back if you are not sure how to do this.

My internet Provided is TWC, and my Modem SURFboard SB6183 and my two routers are airport extreme. up to 50 Mbps and ready to upgrade to 300 Mpbs on June 2015.

Unfortunately, the WAN port on the AirPort Express will only support up to a 100 Mbps connection, so the maximum speed that you have with any device connected to an AirPort Express will be 100 Mbps.

Yes, although you do not really need to disconnect the power connection.....but it will not hurt if you want to do it the way that you have listed.