You can copy either one assignment or all assignments from one course to another. You should have "teacher" role in both courses to perform this operation.
Select "Edit Assignments" in the top bar -
Then select "Copy" from the bottom of the list of assignments -
Select "Course" and then should present a list of all the courses where you have the teacher role -
Select the course and then select "Select assignment" which should present you with a list of assignments in that course and also an option "All assignments" at the top -
Selecting "All assignments" will copy all the assignments from one class into another. Please note that it might take a few minutes for the copy to be successfully completed.