Backup course in Moodle v1.9 and restore in Moodle v3.4

I would like to make possible our teachers to migrate seamlessly their Moodle v1.9 courses to our new Moodle v3.4 site.
Both Moodle v1.9 and Moodle v3.4 sites are on the same server.

So where should I backup a Moodle v1.9 course, so a Moodle v3.4 teacher to be able to pick up and restore?

I'm looking for the easiest solution, but I don't mind to do some custom changes in the code, if needed.

Thanks,

Konrad