I have radius server, all customer end devices and Wireless devices are connected through with Cisco switch. And before server It connected with Dude server installed on Mikrotik CCR-1009.
What want here is Dude need to monitor the devices those are connected behind that server, so i need to open 161/Udp SNMP port on Mikrotik CCR-1009.

How can I open that port on Mikrotik, can anyone suggest me? 

Is hear anyone else who can help on this ?  

See ip firewall nat. Add rule with dstnat action. In filter add rule accepting the dst natted connection in forward chain.