How to copy only updated or newer files

I am trying to create a PowerShell script to copy new and modified files from the source folder to the destination folder. I am able to copy the new file with the given script but also want to add the condition for the modified file also. Can anyone help me to achieve this.

$Sourcefolder = "C:\Users\parveen.kumar\Downloads\Source"
$Desifolder = "C:\Users\parveen.kumar\Downloads\desi"

$GetFiles = Get-ChildItem -Path $Sourcefolder
$BackUpImagesFiles = (Get-ChildItem -Path $Desifolder).Name

foreach($image in $GetFiles)
{
    $fileName = $image.Name;
    if($BackUpImagesFiles -notcontains $fileName)
    {
        Copy-Item $image.FullName -Destination $Desifolder
    }
} 

You can use Get-Item to find if there is a file with that name already in the destination folder or not.

If not OR the file you found is older that the one in the source folder, copy the file.

Something like this:

$Sourcefolder = "C:\Users\parveen.kumar\Downloads\Source"
$Destfolder   = "C:\Users\parveen.kumar\Downloads\desi"

Get-ChildItem -Path $Sourcefolder -File | ForEach-Object {
    # test if there already is a file with that name in the destination folder
    $existingFile = Get-Item -Path (Join-Path -Path $Destfolder -ChildPath $_.Name) -ErrorAction SilentlyContinue
    # if not existing or the existing file is older than the one in the source folder, do the copy
    if (!$existingFile -or $existingFile.LastWriteTime -lt $_.LastWriteTime) {
        $_ | Copy-Item -Destination $Destfolder -Force
    }
} 

Based on your comment, if you want to keep a copy of the file that was already in the destination folder, you can change to:

$Sourcefolder = "C:\Users\parveen.kumar\Downloads\Source"
$Destfolder   = "C:\Users\parveen.kumar\Downloads\desi"

Get-ChildItem -Path $Sourcefolder -File | ForEach-Object {
    # test if there already is a file with that name in the destination folder
    $existingFile = Get-Item -Path (Join-Path -Path $Destfolder -ChildPath $_.Name) -ErrorAction SilentlyContinue
    # if a file already exists AND is older than the one in the source folder, do the copy
    if ($existingFile -and $existingFile.LastWriteTime -lt $_.LastWriteTime) {
        # rename the existing file first before you overwrite with a newer file from the source folder
        # for demo, add the file's last modified date to its name
        $newName = '{0}_{1:yyyy-MM-dd HHmmss}{2}' -f $existingFile.BaseName,
                                                     $existingFile.LastWriteTime,
                                                     $existingFile.Extension
        $existingFile | Rename-Item -NewName $newName -Force
        $_ | Copy-Item -Destination $Destfolder -Force
    }
    elseif (!$existingFile) {
        $_ | Copy-Item -Destination $Destfolder -Force
    }
} 

Another way as you suggested is to Move the existing files into another backup folder instead of renaming them first:

$Sourcefolder       = "C:\Users\parveen.kumar\Downloads\Source"
$Destfolder         = "C:\Users\parveen.kumar\Downloads\desi"
$BackupofDestfolder = "C:\Users\parveen.kumar\Downloads\just"

# make sure the destination and backup folders exist before trying to copy or move files there
$null = New-Item -Path $Destfolder -ItemType Directory -Force
$null = New-Item -Path $BackupofDestfolder -ItemType Directory -Force

Get-ChildItem -Path $Sourcefolder -File | ForEach-Object {
    # test if there already is a file with that name in the destination folder
    $existingFile = Get-Item -Path (Join-Path -Path $Destfolder -ChildPath $_.Name) -ErrorAction SilentlyContinue
    # if a file already exists AND is older than the one in the source folder, do the copy
    if ($existingFile -and $existingFile.LastWriteTime -lt $_.LastWriteTime) {
        # move the existing file first before you overwrite with a newer file from the source folder
        $existingFile | Move-Item -Destination $BackupofDestfolder -Force
        $_ | Copy-Item -Destination $Destfolder -Force
    }
    elseif (!$existingFile) {
        $_ | Copy-Item -Destination $Destfolder -Force
    }
}