as a reminder:
with standard SHIFT + TAB in the game the Steam overlay and thus the guides can be showed up.

source map: https://www.farming-simulator.com/cms/uploads/news_68ca5660d1c36.jpg
source screenshots: DjGoHam Gaming, All Collectible Locations & SURPRISE! | Highlands Fishing Expansion | Farming Simulator 25. https://www.youtube.com/watch?v=jeTv1PkOPdo
numbers by me for your convenience
- at point 3, you can go up to the castle; at the top, you will find a book in which all entries can be read again.
- after you have collected them all, a pirate ship will appear north of point 3 (outside the map, "flying to it’ possible)