How do I find my MacBook Pro's IP?

Default setting of the Router Firewall is to DISCARD all unsolicited accesses to every port on your Network. You will need to Open the correct Port (essentially open a Hole in the Router Firewall) and instruct the Router to forward packets for that port to one specific computer on your Network.

You really can't forward requests to multiple devices on your network. You need to pick ONE.

-OR- use central repository on the Internet (akin to an email server) and pick up your messages remotely.

-OR- create your own local repository on one internet-accessible Server-computer on your network, and pick up messages from that one server.

Once port forwarding and a place for messages to land has been established, you can see your Router's 'Other' address (its Internet-visible address) in its internal configuration information, or by using https://www.whatismyip.com/

Remember that your ISP could change that address, and you will have to adjust.

what IP address you want depends on why you want to know.

The literal answer is seen in

System preferences > network > wi-Fi.

it is extremely likely to be 192.168.1 xxx which is a strictly private IP address used on private networks by Millions of users worldwide, and is unreachable from the Internet at large, by design.

Your Router acts as your agent in all transactions with the Internet at large. Your Router uses Network Address Translation and a State-wise firewall to keep your computer's actual IP address invisible and un-available.

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