You can easily move an enrollment from one course to another by following the steps below.
TIP: it's best to have the course ID for the new course you are moving the enrollment to noted down somewhere, unless each of your courses have a different title so you can easily differentiate between the courses.
1. In the original course that you want to move the enrollment from, click on the Enrollments tab.
2. Click on the Enrollment ID of the enrollment you wish to move.
3. Click on the 3 vertical dots in the upper right and chose Move Enrollment
4. Enter the Course ID or type in the title of the course you want to move the enrollment to and select it in the dropbdown.
5. Click Move and you're done.