Android Studio: Generate Signed Android App Bundle > Save Key with name your_alias.jks (for example YourApp.jks) to any location on your PC > and open CMD and type this:
Code:
"C:\Program Files\Android\Android Studio\jbr\bin\keytool.exe" -exportcert -rfc ^
-alias [your alias] ^
-file "[your location of key]\upload_cert.pem" ^
-keystore "[your location of key]\[your alias].jks"
"C:\Program Files\Android\Android Studio\jbr\bin\keytool.exe" -list -v ^
-keystore "[your location of key]\[your alias].jks" -alias [your alias]
(change text in brackets to your location and/or alias)
And upload .pem file to Google Play, above is instruction how to do this in Google Play.