It is docked at the end of the location bar (where you type web addresses) and is changed so that it is a reload button with an arrow once a web page is loaded but a stop button with a cross whilst a page is loading.

If you really want the old type buttons back it is possible to get something similar using the customise option. (whether you get or two buttons or one combined depends on the position and order of the buttons.)

• see also common questions after updating firefox

Thank you. Now I see it.

Glad to have helped.