Unfortunately, option A doest not work anymore, details here: Migrate tool stoped working in 5.1 - #9 by pmlvl
You have to create a “fake” project folder, with Config, Content and *.uproject in it, and only then it will let you migrate assets. 
Unfortunately, option A doest not work anymore, details here: Migrate tool stoped working in 5.1 - #9 by pmlvl
You have to create a “fake” project folder, with Config, Content and *.uproject in it, and only then it will let you migrate assets.