Another way to look at it.
Another way to think of it is that, in our sky, the Moon and Sun appear the same size. It takes about 10 Jupiter diameters to equal the Sun’s diameter. Mars is 0.5 Au’s from the Earth vs. the Sun’s I AU distance from the Earth.
So at one AU, Jupiter would have about a 1/10 the Diameter of the Moon in our skies. At Mars’ 0.5 AU, Jupiter would have a 1/5 the Moon diameter in our skies. Its disk would be easily visible to the necked eye, as would its moons. Jupiter’s moons are not much smaller than Mars, so some details would be seen in amateur scopes.