[tor-relays] obfs4 bridge port question

I am looking at the post install instructions here after putting up my first bridge: https://community.torproject.org/relay/setup/bridge/post-install/ and thought I would try out the bridgeline for it.

Bridge obfs4 <IP ADDRESS>:<PORT> <FINGERPRINT> cert=<CERTIFICATE> iat-mode=0

I have all the parts mentioned in the text except for <PORT>. I have ExtORPort set to auto, so I never picked a port in my torrc. How do I get there from here?

TIA,

--Torix

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