Can this device expand the WiFi area between two different buildings?

@Rani,

You can check: Specifications

A set of two Multy X units can cover up to 5,000 square feet.

But it is wireless signal and interference from other networks/appliances/wall could be reduce the coverage. What is the distance between two buildings?

@Rani,

Do you mean 30,000 meters? (= 30 kilometers)

I think the distance is too far. As far as I know, Multy X is supported 3 units for maximum and can cover up to 7,500 square feet currently.

I checked the specification, the coverage is 464 square meters.

It should be able to meet your requirement (20 meters). But actual data transfer rates/coverage may vary from network conditions including: network traffics, building site material/construction/Multy X place, interference from other wireless devices and other adverse factors.