Hey Thomas,
The form will work with the embed code. But if you want to do any tracking on visits to the page, or use the webpage as a constraint to track "filled out form on Page X", you need to have the munchkin code on the Unbounce page in addition to the code to embed the form.
When you're editing the Unbounce landing page, there should be a javascript button on the bottom left. Click it and add your munchkin code.
For instructions on where to generate your munchkin code to add to external sites, check out this doc: https://community.marketo.com/MarketoArticle?id=kA050000000KyqXCAS
I used asynchronous code option for quicker page loads.
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