Вот команда из одной строки для того же.
keytool -importkeystore -srckeystore <MY_KEYSTORE.jks> -destkeystore <MY_FILE.p12> -srcstoretype JKS -deststoretype PKCS12 -deststorepass <PASSWORD_PKCS12> -srcalias <ALIAS_SRC> -destalias <ALIAS_DEST>
Объясняя параметры:
MY_FILE.p12: path to the PKCS#12 file (.p12 or .pfx extension) that is going to be created.
MY_KEYSTORE.jks: path to the keystore that you want to convert.
PASSWORD_PKCS12: password that will be requested at the PKCS#12 file opening.
ALIAS_SRC: name matching your certificate entry in the JKS keystore, "tomcat" for example.
ALIAS_DEST: name that will match your certificate entry in the PKCS#12 file, "tomcat" for example.