Is this a movie or a book question?
Regardless, Professor McGonagall instructs the Slytherins to leave the Great Hall with Filch, but does not direct Filch to take the Slytherins to any particular place.
‘Thank you, Miss Parkinson,’ said Professor McGonagall in a clipped voice. ‘You will leave the Hall first with Mr Filch. If the rest of your house could follow.’
Harry heard the grinding of benches and then the sound of the Slytherins trooping out on the other side of the Hall.
Harry Potter and the Deathly Hallows - Chapter 31, The Battle of Hogwarts - Page 491 - Bloomsbury
In the movie, Professor McGonagall directs Filch to take the Slytherins to the dungeons. As the Slytherin dormitories are in the dungeons, it's unclear whether Filch is supposed to lock them up in their dorms, or if there is another dungeon the Slytherins are to be locked up in. The movie clip you provide obviously doesn't clarify which dungeon was meant.
Book: It's not stated.
Movie: One of the Hogwarts dungeons