Take a quick peek at Kepler's laws.
http://hyperphysics.phy-astr.gsu.edu/hbase/kepler.html
"The square of the period of any planet is proportional to the cube of the semimajor axis of its orbit."
P^2 = a^3
P is measured in years, and a is the semimajor axis measured in AU (mean distance Earth-Sun, ~150million kilometers)
So, 380^2 = 144400, and 144400^(1/3) = 52,5
Of one of the stars were the sun, the other would be 25% farther out that Pluto (Sun-Pluto = 40AU)
The answer to your other question is: it depends.
It depends on the surroundings. Two bodies orbit eachother if no other external force of gravity is strong enough to pull them from eachother. Since gravity is infinite in reach, you could in theory have two stars orbiting eachother at a distance of several billion lightyears if there was nothing else closer by.
Stars are often born in groups, and naturally form multisystems of stars. Then, some stars "capture" other stars. I don't know the ratio of the two.
I've heard somewhere that most stars live in doublestar systems but I can't vouch for it.
For something to not be part of our galaxy, they would have to be dominated by some external force of gravity, another galaxy. I don't think there are many single/double/multi stars between galaxies, where should they have formed?