As of now it is not yet officially confirmed.
Thus far mayor of Amsterdam has not allowed quarter-finals nor semi-finals, as matches with Dutch participation start at 22:00 (10pm) and can end as late as 01:00 (1am), which is too late according to Amsterdam's bureaucrats. So one thing for sure, you will not be able to watch the semi-final on the big screen at Museumplein.
Meanwhile, the Netherlands is gearing up for the match, although big
screens showing the match will be hard to find in Amsterdam.
The one on the Museumplein has been removed and will not return unless
Oranje reaches the final, and other borough councils have refused to
licence outdoor screens. Supporters will have to head for the
Arenapark is a park by the Bijlmer ArenA, you can get there from the center by metro.
As for the finals, there is no official decision yet. City hall's official page about World Cup (in Dutch) only mentions semi-finals for now. On the other hand the mayor has mentioned in a TV interview that it might be possible to have finals on Museumplein.
Museumplein is in the city center. For the past matches the location had 3 screens. Entry is free, however you're not allowed to consume alcohol other than bought there.
UPDATE: As the Netherlands didn't make the final, it is now official.
De troostfinale, op zaterdag 12 juli, en de finale, op zondag 13 juli,
zullen niet op een groot scherm te zien zijn op het Museumplein.
The consolation final, on Saturday, July 12th, and the final on
Sunday, July 13th, will not be seen on the big screen at the Museumplein.
Also, no mention of Arenapark at all, which might suggest it won't be shown there either.