All you need to do is open Google Classroom and select the three dots in the upper right of the "card". Then select copy and then you have the options to rename the Class, Section, Subject, and Room.
Important pieces of information to point out is that classwork posts are saved (as drafts). Also, the following will not be copied :
Deleted classwork items
Students and co-teachers
Attachments that you don’t have permission to copy
Embedded below is a 1 minute and 13 second YouTube tutorial.