Packback can be found a few ways in an Original course.
In an assessment, it can be found under Tools>>More Tools>>Packback, as seen here:
If you would like to add it to the course menu, you can find it by using the Add Menu Item button, Then choose Tool Link:
If you would like to add it to the course menu, you can find it by using the Add Menu Item button, Then choose Tool Link:
then, from the drop-down menu, choose PackBack.
This will create a link in the course menu.