After turning on the printer, do as in the image and get a slip printed from the printer. It contains the network information of the printer along with other hardware details depending upon the printer model.

Check the image for arrow pointing to the buttons for getting the IP and hardware detail slip out. In some a pin is needed to press the button and in other a button is present depending on model of printer. Warning: Do not long press the button as it will reset the printer. Just click the button once.

Here are some examples of slip printed from different printers.