Hello Sepideh
Port 3323 is the port used by the RPKI-to-Router protocol (RTR). This is the protocol used to allow BGP routers to communicate with the Routinator server. So for communication between the BGP routers and Routinator, 3323 is the correct TCP port.
The 8323 port is used to connect to the GUI of the Routinator. So from your PC, on a web browser you would include the port number to be used. For example, in this lesson, Rene used: docker1.nwl.ai:8323.
These port numbers are reaffirmed at this related Routinator documentation:
https://routinator.docs.nlnetlabs.nl/en/stable/daemon.html
I hope this has been helpful!
Laz