There are several online tools that allow you to see who is hosting a website. After you have transferred your website to the new host, you can use any of these tools, and they will show you the name of the web hosting company hosting your website.
If it hasn’t been long since you migrated your website and made changes to your domain name server (DNS), then chances are that your site may still load from your old host. Domain name changes can take up to 48 hours to fully propagate.