unable to get .pem file from keyStore through cmd prompt!!

hi unity community .i am a unity game developer. i am trying to get .pem file through command in order to enable app signing
“java -jar pepk.jar --keystore --alias --en
cryptionkey= --output=”

when it asking for keystore passward i enter… then it ask for alias passward to enter which is same as keystorepassward… but it is giving error : no key for alias : [aliasname]… plz help

I am also using the same in thing but in cmd it shows the error.
its not even asking for the keystore password and just showing the error.
what is the location of java -jar ? i mean to say you start from C\programfiles/java or its a random path.?