powershell Trying to format a csv file column to a given number of decimal places

I have a csv column called Volume that I am trying to reformat to a given number of decimal places. Here is what I have from ChatGPT but I am getting errors:
The property cannot be processed because the property "Volume" already exists.

$data = Import-Csv $AF
$columnName = "Volume"
$numberOfDecimalPlaces = 2

# Format the column with the specified number of decimal places
$newData = $data | Select-Object *,@{
    Name = $columnName
    Expression = { "{0:N$numberOfDecimalPlaces}" -f [decimal]$_.$columnName }
}

$newData | Export-Csv $AF -NoTypeInformation

Any help in formatting the column would be appreciated. I have a number of them to format.

>Solution :

By using *,@{Name='Volume', ...} you are telling it to use "All the Columns, including Volume, AND then also add ANOTHER ‘Volume’ column"

# Load CSV file in a collection
$Csv = Import-Csv $File

# self-loop through the collection, changing the value as you need
# BEWARE: the decimal separator will be in the style of the [cultureinfo]::currentculture value
$Csv.Foreach({ $_.$Column= "{0:N$numberOfDecimalPlaces}" -f [decimal]$_.$Column})

# export back the collection
# you can skip -NoTypeInformation if you are using Powershell 6+
$Csv | Export-Csv -Path $File -NoTypeInformation