I am glad you came to your senses to get a Mac.
On your Mac simply download and install Xampp for Mac.
Navigate to /Applications/XAMPP/xamppfiles/ you will see a folder htdocs. This is the document root, where all you pages are.
There are also four items in it, favicon.ico, index.php webalizer and xampp, leave them intact and copy your all pages from your Windows Xampp document root to this directory. You might need to set the permissions of your pages.
If you have any MySql database, on the Window machine, use PHPMyAdmin to export them, then copy the data files to import them on your Mac Xampp. Of course if you have any customized configurations, you would need to redo them. You might be able to reuse the config files from your Windows installation, but it's always better to configure afresh since you are doing a fresh installation.
Hope it helps.