Need Help to re-link with external container storage with a runtime solution

Hi everybody,

I created a runtime  for a customer that wants to access an older solution for reference only.   

The solution has external container storage that i cannot access anymore.  The original path was outside the database so it's very hard to re-create a relative path.

Tried to drag new files in containers doesn't seem to work

Is there a config file somewhere in the runtime that i can use to edit a new path?  Any other ideas?  

I have no access to the admin password of the original solution.

Thanks!