Arduino network

Hello , i want to connect number of arduinos to a single arduino separated up to 30 m , using wired connection ? can it achieved using UART ?

Yes

please mention , can the wires be extended up to 30 m without signal attenuation , and how to connect several arduinos to only a pair of Tx & Rx pins ? please help

There are many ways to do this. One way is to:-

You extend wires by using RS485 buffers. You chain each TX to the next processor's RX, then you pass messages round in packets. Each processor has an ID number the processor only responds to message packets that are tagged with it's number.