Finally found the mod I was looking for: "Billboards" (yes it's for parkitect).

But the problem is that I don't know how to install it and it's not on the steam workshop.
Had to find it of the old Nexus mods, but the nexus launcher no longer exists.

So now I am confused as to how can I install it if it's not on steam workshop and without Nexus manager.

Can some one lend me a hand.