To convert EML files to PST using PowerShell, you can use the Import-Mailbox cmdlet. It needs some coding knowledge as well. Here's how to do it:

1. Open Windows PowerShell on your computer.
2. Use the following command to install the required module for working with Outlook:

Install-Module -Name PSTCmdlet

1. Once the module is installed, use the following command to create a new Outlook session:

$Outlook = New-Object -ComObject Outlook.Application

1. Navigate to the directory where your EML files are stored using the following command:

Set-Location "C:\path\to\eml\files"

1. Use the following command to convert the EML files to PST:

Get-ChildItem -Filter *.eml | ForEach-Object { $MailItem = $Outlook.CreateItem(0); $MailItem.Import($_.FullName, 1024); $MailItem.Save() }

1. This command will import each EML file to Outlook and save it as a new email message.
2. Once all EML files are imported to Outlook, use the Export-Mailbox cmdlet to export the messages to a new PST file: Export-Mailbox -Identity "your_email_address" -PSTFolderPath "C:\path\to\new\pst\file.pst"

This command will export all the messages in your Outlook mailbox to a new PST file. In this way, you can convert your EML files to PST using PowerShell. However, for an easier conversion process, you can use professional Regain EML to PST converter.

For detail guide, read this blog post: https://www.regainsoftware.com/how-to/convert-eml-to-pst-manual-guide.html