Windows 2012 Powershell Script for file/folder permissions accross MS AD Forests

I have two AD Forests with users/groups in both. Current file server is in old forest domain and need to add the new forest domain users and groups to the files/folders. ADMT was used but admin did not copy SID information or migrate the file server at the time of the new forest creation. Will probably need to query AD for SAMAccountNames in powershell as groups and usernames should be same with a few exceptions. There is a powershell script for reference that does the mapping but it creates a separate folder structure and isn't working in my environment they way I need it to. You will not have access to the server so will need your own test environment but I can also test the script as needed. Example script I found below: [login to view URL]