Hi there @BRUNO13, thanks for posting your question here!
You can move the Dropbox folder from one location to another by following the steps mentioned in this article.
There, you'll also find some pointers to keep in mind when moving the Dropbox folder to an external drive.
However, I also wanted to mention that you could use selective sync, instead of moving the whole Dropbox folder.
Could you check this link out for more info on it and let me know if that will do the trick?
Looking forward to hearing back from you!