Hello Mr. Pintu

You do not need the IP Adress of the Panel. If you do a reset to factory Settings then you need only the Mac Adress and its printed at the back of the Panel or in the Boot screen.

Look here is a Manual for Simatic Prosave to do a Reset at a MP377:

https://support.industry.siemens.com/cs/ww/en/view/19701610

If you only do not know the IP Adress and the Panel is working well then you could use Tools like "advanced IP Scanner" to scan the network in order to read out the IP Adress.

Bye Murof