Welcome to the forum.
This will depend on how you set up the Project, when you began.
I create a unique folder/sub-folder, for each Project, and everything is in that hierarchy, the Scratch Disks, Copies of all Assets, etc.. When done, I just Delete the Project's folder, and all sub-folders go with it.
One consideration is if there is a chance that you will ever need to revisit that Project, you might use the Project Archiver first, to get a copy of the entire Project onto, say an external HDD - just in case.
How did you set up the Project's folders/sub-folders?
This ARTICLE will give you one workflow.