I would like to know if you can connect an external graphics card to a notebook (Microsoft Surface book 2) which no Thunderbolt 3 has.
No. Almost impossible. In order to be able to connect a graphics card, you would need a PCIe connection. As far as I know, the Surface Book is difficult to open and has no accessible mini PCIe ports. But you could try cloud services like Shadow.
That's why I no longer buy MS laptops…
With an external graphics card you don't drive so well anyway. It can never develop its full potential.
If you choose a connection other than Thunderbolt anyway, then it's over.