I can see and reach to folder to clean it, can someone help please?
The .dropbox.cache folder is a hidden folder and won't be visible unless you have your operating system set to show hidden files.
Also, there's usually no need to clear this folder. Dropbox uses this folder to store chunks of files as they're syncing and as a way to be able to recover files you've deleted (for a short time, anyway). Dropbox manages the folder on its own.