There are 3 main ways through which you can find someone’s IP address:
CMD/ Terminal:  On Windows OS open CMD and type ping website address and hit enter.
Email Headers: Emails don’t just carry a message but also other details too. Navigate to email headers in Gmail by pressing the … icon and then clicking down the arrow and finally clicking on the show original will open a new window containing the sender’s details.
Look-up tools: There are a number of IP lookup tools available on the internet.