i've managed to convery it once years ago with a converter that i can't find anymore,
i've done it again recently, but you need an xbox one with the "new" version of minecraft and a retail copy of xbox one edition
upload your save from xbox 360 to xbox one
open minecraft xbox one edition and download your save there, playtest it to make sure it doesn't crash
open the "new" minecraft and import your xbox one saves, playtest it again so it doesn't crash
get a realms subscription and upload your world there (i used my 30 day free trial)
head over to PC and download the world from there
if it's the java version of minecraft then you'll have to get horizon or whatever it's called, put your save on a USB stick, and figure things out from there, been years sinc ei did it
nope, they constantly change