How do I give the following responsive information in the .info file?
Your D7 declarations have the effect of placing the media query in the markup, and I think you want to replicate that method. You can do this in the library declarations, e.g.

stylesheets[all and (max-width: 760px)][] = css/mobile.css


Becomes:

mobile:
  version: 8.x-1.0
  css:
    layout:
      css/mobile.css: { media: all and (max-width: 760px) }


Note I am assuming this is for layout, hence my use of the "layout" SMACCS category for this library.

Personally I don't really bother with such things and write the media queries in the CSS, if you have many media queries you're going to have a lot of extra http requests if you're always splitting files based solely on breakpoint.