How to transfer submissions from a concluded course to a new course?

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I am trying to transfer students' submission from my Sandbox that I concluded because my actual course was finally created after three weeks into the semester. I was able to export the grades and didn't know about the exporting of submissions, so now the students are seeing assignments in their todo's that have already been done. I also have a late penalty on my grade book making them resubmit the assignments a nightmare of overriding the grades after being submitted. Is there a way to transfer submissions in a concluded course or is there a work around with the missing submissions the students are seeing?