Start by logging into your Mailchimp account. Navigate to the list or audience whose data you want to export. Use Mailchimp’s built-in export feature to download your audience data as a CSV file. This file will contain all the necessary data fields you need to transfer.

Log into your Google Cloud Console. If you don’t have a project set up yet, create a new project. Make sure to enable billing for your project, as Google Cloud services, including Pub/Sub, require it.

Within your Google Cloud project, navigate to the “APIs & Services”� section and search for “Pub/Sub API.”� Enable this API to allow your project to use Google Pub/Sub services.

In the Google Cloud Console, go to the Pub/Sub section and create a new topic. A topic is a named resource to which messages are sent by publishers. Give your topic a relevant name, as this will be where you publish your Mailchimp data.

Create a service account in your Google Cloud project to authenticate API requests. Go to the “IAM & Admin”� section, create a new service account, and download the JSON key file. This file will be used for authenticating your scripts that interact with Google Pub/Sub.

Write a Python script (or use another programming language of your choice) to read the CSV file and publish the data to your Pub/Sub topic. Use the Google Cloud Client Library to authenticate using your service account’s JSON key and publish messages to the topic. Each row in the CSV can be published as a separate message.

Example Python snippet:
```python
from google.cloud import pubsub_v1
import csv
import json

# Set up Pub/Sub client
publisher = pubsub_v1.PublisherClient.from_service_account_json('path/to/service_account.json')
topic_path = publisher.topic_path('your-project-id', 'your-topic-name')

# Read CSV and publish to Pub/Sub
with open('path/to/mailchimp_data.csv', newline='') as csvfile:
reader = csv.DictReader(csvfile)
for row in reader:
message_data = json.dumps(row).encode('utf-8')
publisher.publish(topic_path, data=message_data)

print("Data successfully published to Google Pub/Sub.")
```

Confirm that your data has been successfully published to the Pub/Sub topic. You can create a subscription to your topic in Google Cloud Console and pull messages to verify the data. Alternatively, use the Pub/Sub emulator for local testing before deploying your solution.

By following these steps, you can efficiently move data from Mailchimp to Google Pub/Sub without relying on third-party connectors or integrations.