Earth to Io.

Km, au , and light years. are almost the same. 1 au equals to 150,000,000 kilometers (km). Light years measure more further, like earth tom galaxy or the nearest star ( not the sun). Kilometers are mainly use between planets, Au is just a better simplify.

NASA's Galileo spacecraft was originally supposed to take only 2 years to reach Jupiter following a direct flight path. It was supposed to launch from the space shuttle Challenger, but after the disaster, NASA decided to give it a slower route that involved several gravitational flybys around Venus and Earth. In the end, it took about 6 years to reach Jupiter. NASA's New Horizons spacecraft, the fastest spacecraft ever launched, took just 13 months to reach Jupiter from Earth.

I do not think humans are able to land on io. Io is full with volcanoes. It is extremely hot and dangerous, one land can kill a person quickly, or might even get melted.

The minimum distance between Jupiter and Earth is 588 million km (365 million miles). Since one light year (the distance light travels in one year) is approximately 5,870,000,000,000 miles, the minimum distance between Jupiter and Earth is 0.0000621 light years.