.. Where can I find those numbers?

One is in the crow's nest on board the ship --

How do I get to the crow's nest?

-- one is revealed when you solve the word search in the journal and then use the pins on the map in the captain's quarters --

How do I solve the wordsearch in the journal?

What am I doing with the map on the wall?

-- and the last one can be found when you sit in the dinghy at low tide.

How do I change the tide?

How do I find the dinghy number?