Most free VPNs won’t make it safer to use Tor. Since Tor is more secure than standard browsers, I can understand why you’d feel safe combining it with a free vpn for dark web. But your ISP knows when you connect to Tor, and it takes a quality VPN to hide this fact. If you’re going to surf the dark web, you’ll need to use a VPN to protect your privacy. This way your ISP and other third parties won’t be able to see you’re surfing the dark web.