Windows 10 itself doesn't have such a toolbar (or, more accurately, 'menu bar'). It's your browser which does - and you've forgotten to tell us which one it is!
However (in all main browsers) if you accidentally hit F11 you'll go to full-screen view and loose the menu bar. As O_G suggests, pressing F11 again will get it back.
If that's not the cause of your problem then your browser has 'forgotten' that you like to see the menu bar at the top of your screen. (Not everyone does). In Firefox (and, I believe in most other browsers) you can get it back by right-clicking at the top of your screen and putting a tick next to 'Menu bar'.