Which lens i need to take these kind of photos?

So which lens will work best for these photos as the ones in this blog jakandjil.com
(i don't mean just the blurry background but the whole photo as it is).it looks wide enough, good depth of field).
will any lens work for it or need any specific like 24-70 mm, 85 mm, 50 mm?
i have nikon d3100

Since none of the images still have their EXIF data, it is not possible to know exactly what lenses were used when shooting these fashion shots, but since most fashion photographers have the 24-70 mm f/2.8 and 70-200 mm f/2.8 lenses as part of their camera system, it would be a fair guess that one or both of those lenses was used.

No fashion photographer would shoot under outdoors conditions using a prime lens like a 50 mm or 85 mm, since composition would require them to establish many different shooting distances from the subject and that is just not practical under those conditions.

In a controlled environment like a studio, sure a prime lens like those you mentioned could be used, but shooting 3/4 or full length shots with an 85 mm on a camera like you have would place the photographer too far from the subject to be able to easily direct them