"There will be two cats there."

Translation: 그곳에서는 두 마리의 고양이가 있을 것입니다.

[dagummace]

Yes, why not 그곳에서 고양이가 두 마리 있일 것입니다?

[Dakota750821]

Both are correct. The order of the words helps to determine the focus and emphasis of the sentence. The later in the sentence a word is, the more important it is.

So, 두 마리의 고양이 puts more focus on the cats, rather than, let's say, dogs.

고양이 두 마리 puts more focus on the number of cats.

The "의" following the 마리 just connects the counter with the corresponding noun.

[Komerinam]

그곳에는 should be better.

[Rose.Melissa]

The noun more commonly comes before the counter word (i.e., 고양이 두 마리 not 두 마리 고양이) Also, it should be 마리 not 마리의 because it is cats not cat's (possessive)

[KarenKaise2]

의 doesn't always function as possessive. This construction is correct. 고양이 두 마리 is more common, but 두 마리의 고양이 is acceptable.

[GeraldMath4]

I am surprised by the 에서. Why not just 에?

[BobaBunny5]

So am I, usually it's just 에 있다.

[GeraldMath4]

Maybe the 을 것입니다 turns it into a happening instead of a state?

[Doldrumz]

What about 저기에 ?