How to identify the type of device, whether the device is a switch, router, printer, Hub etc?

I have discovered the Network and some nodes are added in the OpenNMS, Now I want to know the information of that Nodes like (router, switch, etc), how we can achieve this ?

You would need to make sure SNMP is setup on your nodes and OpenNMS is configured to collect from them. It won’t pull those labels specifically, but there typically will be other info about the device that will be collected that will get you close.