Hi,
This is more a KAFKA question than a Pubsub one. If you want to send a KAFKA messages to a PubSub, you may need to use the CloudPubSubConnector [1] .
You can also check this good article [2] see method 2 where pubsub is used to collect messages from KAFKA.
/Samar
[1]:https://github.com/GoogleCloudPlatform/pubsub/tree/master/kafka-connector
[1]: https://medium.com/google-cloud/kafka-to-bigquery-using-dataflow-6ec73ec249bb