wooassist

This plugin adds a custom field in the checkout page to ask your customers where they heard about your store.
This plugin also offers an “Other” field where your customer can provide a specific answer in a separate textbox.
Features:
<ul>
<li>Easily change the labels and choices for the custom field in the checkout page.</li>
<li>View reports on the “Reports” section in WooCommerce.</li>
<li>Enable/disable the custom field to be required on checkout.</li>
<li>Enable/disable the “Other” field.</li>
<li>Modify order statuses you want to include in the reports.</li>
<li>Export Orders with Customer Source field</li>
</ul>

Where Did You Hear About Us Checkout Field for WooCommerce

Adds a custom field in the checkout page to ask your customers where they've heard about your store.

Where Did You Hear About Us Checkout Field for WooCommerce vs WooCommerce