I have this in an ActiveMQ config:
First convert to p12:
openssl pkcs12 -export -in [filename-certificate] -inkey [filename-key] -name [host] -out [filename-new-PKCS-12.p12]
Create new JKS from p12:
keytool -importkeystore -deststorepass [password] -destkeystore [filename-new-keystore.jks] -srckeystore [filename-new-PKCS-12.p12] -srcstoretype PKCS12