You can try going to analytics > classic insights. From there run a form submission report and export the data to Excel. Then you can remove duplicates, testing et cetera and sort by column.
Thanks Ben. My primary goal is to understand landing page conversion rate by source. I don't think I can match form submissions to visits by source.
I think you have a few options here. You can either manually tag each e-mail for source, medium, campaign, content or you can set this up: Basic Web Analytics Integration with Eloqua
Then you just need to follow this post: