So you want to delete the contents of a folder without deleting the folder itself? Would that also include sub-folders within that folder?
Simply enter cd <path to directory> at the prompt to make the required directory the target of the next command. Then, after verification that this is the correct directory and that you do indeed want to remove its contents, enter del *.* at the prompt. This should delete its contents, but not the directory itself. Please note that content cannot be easily recovered, which is why I asked you to verify the location first.