Marinelli theme is still not yet ported to Drupal 8 yet. So, you won't be able to migrate Marinelli theme to Drupal 8. But you have an alternative option.
You can use any other theme which is already ported to Drupal 8. There are more than 218 themes are available in D8. Refer link: https://www.drupal.org/project/project_theme/index?project-status=full&drupal_core=7234