How to find out stolen phone of android by using IMEI number?

Find your device through the IMEI number is not really a thing an everyday citizen can do.

Googles find my device is about the best you can do. If the internet and location are off then things will not work. There are website that state they can track based on your IMEI number but then why would they also need your phone number. It is also very doubtful a carrier would give the third party website access to their proprietary information and tools.

Your IMEI number should be consider sensitive information not freely given out to unknown sources.

Another thing you can try is view location history through Google Maps Timeline. If the find my device or location history does not work.

Depending on the laws of your country contact the authorities and file a report. They can then subpoena your carrier to get the location or last known location of the device by triangulating based off their towers.