Open the OLD Google Classroom
Open the Assignment in the OLD Google Classroom
Open the ATTACHMENT (file) in the OLD Google Classroom
This is the file, note the "last edit" comment. By opening it, this will be listed a "Recent" and make it easier to find when you add it to the NEW classroom
Open the New Classroom
Open the New Assignment where you want to add your file to
3. Select "+ Add or create"
4. Select "Google Drive"
5. Your file will be under the "Recent" heading, be sure to select the correct file
6. Select "Insert" when ready
7. Now your old file is part of the new assignment