For Windows User: C:\Users\USERNAME\.android\debug.keystore
(Replace USERNAME with your actual PC user name)
For Linux or Mac OS User: ~/.android/debug.keystore
After you will get SHA1
by below Code using Command Prompt:
keytool -list -v -keystore "C:\Users\USERNAME\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android