Kafka Connector always works as a single task

I am trying to transfer data from oracleDB to mongoDB using kafka. So I configured the kafka cluster like the picture above. I know that adjusting partition and tasks.max allows parallel processing. However, when I run the connector, it always runs as a single task and cannot be processed in parallel. Are there any additional settings I need to do?

Here is what I configured.

1. Topic creation

bin/kafka-topics.sh --create --bootstrap-server 127.0.0.1:9092,127.0.0.2:9092,127.0.0.1:9093 --partitions 3 --topic topicA

2. connector config

   {
   "name": "rawsumc-source",
   "config": {
       "connector.class": "io.confluent.connect.jdbc.JdbcSourceConnector",
       "connection.url": "jdbc:oracle:thin:@127.0.0.1:1521/orcl",
       "connection.user": "test",
       "connection.password": "test",
       "topic.prefix": "topicA",
       "mode": "bulk",
       "poll.interval.ms": "360000000",
       "numeric.mapping": "best_fit",
       "tasks.max": "10",
       "connection.type": "lz4",
       "query": "select CAST(NO_TT AS NUMBER(10,0)) AS NO_TT,CAST(NO_SEQ AS NUMBER(10,0)) AS NO_SEQ,DNT_CLCT from table_a",
       "name": "rawsumc-source"
   },
   "tasks": [
       {
           "connector": "rawsumc-source",
           "task": 0
       }
   ],
   "type": "source"}
   

According the docs:

tasks.max - The maximum number of tasks that should be created for this connector. The connector may create fewer tasks if it cannot achieve this level of parallelism.

Using a custom query for JdbcSourceConnector limits you to a single task.