Setup Nvidia 1070Ti external GPU

I have Dell XPS 9570. I am trying to connect egpu using thunderbolt 3 port.

OS: Ubuntu

My laptop has an internal 1050Ti graphic card. So the system is not recognizing the external GPU. I tried to disable it from the bios but I did not find any options that are suggested online. The GPU is not detected in both ubuntu and windows OS.

How can I fix this issue?