I do not know if I understood the question correctly, you want to get the phone UDID. Another option is:
Connect the phone to the computer (Windows) via USB, download and install iTunes, then configure the connection.
After starting the program, we choose the device from which we want to read the identifier. Then click on the serial number until the label with the UDiD number appears. When the UDiD number appears, right click on it and select copy.