Convert Sharepoint Choice Column to Lookup Column - PowerShell

Convert-Sharepoint-Choice-Column-to-Lookup-Column.ps1

#Install PnP PowerShell in your local machine https://github.com/pnp/powershell

$SiteUrl = "https://ssite.sharepoint.com/sites/SPSiteName";
$ListMainName = "List Name";
$ListCompaniesName = "Lookup List Name"

# Login using Web
Connect-PnPOnline -Url $SiteUrl -UseWebLogin

#If we can't use PnP
#$context = New-Object Microsoft.SharePoint.Client.ClientContext($SiteUrl);
#$context = Get-PnPContext

# Retrieve the lists

$ListCompanies = Get-PnPListItem -List $ListCompaniesName -ErrorAction Stop
#If we require to limit the fields for a big List
#$fields = "Id","Title","Company","CompanyTmp";
$ListMain = Get-PnPListItem -List $ListMainName -ErrorAction Stop

# Enumerate the list and update column
$ItemCount = $ListMain.Count;
"`Main List contains $itemCount items ...`n"

$i = 1;
ForEach ($Item in $ListMain) {
    #$Item["CompanyTmp"]
    #if( ($Item["CompanyTmp"]) -and ($Item["Company"] -eq $Item["CompanyTmp"]["LookupValue"])) {
    #    break;
    #}
    #$Item.FieldValues;
    
    # Match choice to lookup
    ForEach ($ItemLU in $ListCompanies) {
        
        $Item["CompanyName"]
        
        If ($ItemLU["Title"] -eq $Item["CompanyName"]) {
          "Updating item: $i of $ItemCount"
          Set-PnPListItem -List $ListMainName -Identity $Item["ID"] -Values @{"CompanyTmp" = $ItemLU["ID"]}
        }
    }
    $i++

    #Break for testing
    #if($i -eq 4) {
    #    "end"
    #    break;
    #}

}