Are there any data from spacecraft that visited that planet? How large the Earth is when viewed from that planet?
It's a tiny blue dot of just about 1.6 arc seconds diameter. Cassini made the most famous image of the "In Saturn's Shadow – The Pale Blue Dot", in remembrance of the first such image from Voyager one: a view of Earth and Moon from Saturn (image: NASA/ESA).
The dark side of Saturn, its bright limb, the main rings, the F ring, and the G and E rings are clearly seen; the limb of Saturn and the F ring are overexposed. The ‘breaks’ in the brightness of Saturn’s limb are due to the shadows of the rings on the globe of Saturn, preventing sunlight from shining through the atmosphere in those regions. The E and G rings have been brightened for better visibility.
Earth, 1.44 billion km away in this image, appears as a blue dot at centre right; the Moon can be seen as a fainter protrusion off its right side. The other bright dots nearby are stars.
JPL shows a few more images, including a zoom image taken of the Moon-Earth-system.
See also the wiki entry on "pale blue dot" as part of the impressive "family portrait" series taken by Voyager 1 in 1990 from a distance of about 40 AU which show most of our solar system planets from 6 billion kilometers distance. Also compare with the successor series taken by the messenger spacecraft 20 years later in 2010 from about the orbit of Mercury.