Get directory to save file

I'm developing a system, and in that system, I generate a PDF report from some information, I'd like to know, how do I open a screen that looks like filedialog , but to select only the directory, so that when you generate the report, the user selects where the report is going to be saved, as if it were those window of selecting where you are going to download a file, what would be the best way to do that?