Getting an external file URL for ARKit use

I want to display .obj/.stl files in augmented reality. I have been able to display objects in AR, as long as the files were initially located in the art.ascnassets folder. However, my ultimate goal is to display obj files located in the Files app on the same iOS device. I planned to accomplish this by extracting the URL of the .obj file, and using the MDLAsset function to convert the URL into an asset, which would later be converted into an object.

The major problem I encountered is extracting the URL. What is the best method to get the URL of an .obj file selected in the Files app? I have tried using UIDocumentPickerViewController, where it launches the Files app on the application. This would allow the user to select the .obj file of their choice, and afterwards the program would convert the URL of that file to an object.