Greetings
I need to publish a port 37777 to access a private device thru internet.

Private device has an Ip 10.20.1.224 it is connected thru a mikrotik that has the network segment 10.20.1.x

This network is connected thru PTP connection to another network 10.20.0.x where it has the Internet connectivity

Do i only have to make a dst nat rule on the mikrotik where the internet connection is and open port 37777
and also open port on the router where the private device is located?

Both routers.

Router A (10.20.0.X)
Router B (10.20.1.X)

You redirect port 37777 from router A to router B, and router B to device with IP 10.20.1.224.