Get-ChildItem -Path D:\Plans |
ForEach-Object {
If ([Int]$_.BaseName -le 1980) { Move-Item $_.FullName -Destination 'D:\1900s\' }
If ([Int]$_.BaseName -ge 2000) { Move-Item $_.FullName -Destination 'D:\2000s\' }
}
This should get you started on the direction you want, but your question isn’t very clear.