Create a QR to outside Website or App

I have a Button in our QB App that creates a Folder for that Child Account name in Dropbox, it then takes the Dropbox Link for that Folder and puts it into a Field in the Child Account Form.  I want a Field that creates a QR Code that takes the person scanning the QR to that Specific Dropbox Folder.

This is the Formula that i have write now, but its not opening the folder.

var text URL = URLEncode(URLRoot() & "db/" & Dbid() & "?a=dr&rid=" & [Dropbox Folder URL]);

"<img src='https://quickchart.io/chart?cht=qr&chs=180x180&chl=" & URLEncode($URL)& "'>"