Thanks for visiting the Community.
To confirm, are you trying to connect your TV with a built-in Chromecast to your mobile hotspot? If yes, you will need two mobile devices for this setup (one will serve as a router and the other to be used to set up your TV with built-in Chromecast). Please note that we do not recommend connecting your device to a mobile hotspot because your TV needs a strong and stable internet connection.
Hope this helps.