@Adhitya,
I am not quite sure what you mean with response topic, but as far as I can tell, you need to use ConsumeMQTT in order to "ingest" data out of the MQTT brokers/topics. If you want to publish within the brokers/topics, you will have to use PublishMQTT.
In both cases, you will have to choose the MQTT Specification Version, where you will have to select something from the following options: v3 Auto, v3.1.1, v3.1.0 and v5.0.
See: https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi/nifi-mqtt-nar/1.21.0/org.apache.ni...