Change the paths to user folders(Shell Folders) with Powershell

Question

How to change the paths to user folders (Shell Folders) with Powershell? Required:

1. get the path to the folder $mydoc = [Environment]::GetFolderPath('MyDocuments') C:\Users\shay\Documents
2. Change the drive letters in a variable $mydoc - C:\Users\shay\Documents to d:\Users\shay\Documents ??
3. Create a folder - d:\Users\shay\Documents ??
4. Copy the folder C:\Users\shay\Documents to d:\Users\shay\Documents ??
5. Set the path to the My Documents system folder - d:\Users\shay\Documents ?? I am grateful in advance for your help.