I HAVE LAST 6 DIGIT OF MY IMEI

Yes.

Find IMEI & Serial No. of the Lost Device

You may use a web browser to get the Serial Number and the IMEI Number. You cannot track using the IMEI number. but you may need it so keep it handy

Log in to https://appleid.apple.com with your Apple ID credentials. All your devices will be listed there. Click on any to get the details.

the only usage your IMEI would be would that you could have your carriers and carriers they work with block the phone from ever being used again, you can't track it or the likes

and for that you need the full number