Hello @abhijeet980
The hyphens in the permanent links are the best way to separate each word and make each link more friendly, without the hyphens you would have a structure somewhat similar to
https://www.google.com/qwertyui45werfgh67tghnjm78fghjkl
Which is difficult for human beings to read, if you want to delete the hyphens you can do it from each of the posts in the permanent link option. But remember that hyphens in links are recognized as separators by Google which helps SEO, that is why all pages prefer to use hyphens to other characters.
