Open the dump1090 output (127.0.0.1:8080) on your RasPi browser. I would recommend installing Planefinder client and dump1090-mutability as they have better visual graphics.
All that can be easily installed by @jprochazka scripts. ads-b-flight-tracking-f21/ads-b-receiver-project-setup-scripts-t36532.html
There’s also another option of using ModesDeco2 instead of dump1090 with basestation and flightroute files.