Question [Q] Motorola KEY.pk8 for moto e exploit apk

Hello Devs... please tell me,
""How to extract KEY.pk8 from system's apk file""
I read on XDA that it can be extracted using PackageManager. but I don't know what is packagemanager and which os it needs to be install and where to find it
I want to create Motorola keystore for signing exploits apk for moto E (experimental)