What you write above are instructions to position the toolbar with the address bar at the top of the bottom of the screen on an Android mobile device, this isn't possible in Firefox on a desktop device if that is what you are trying to do. This is merely about tapping the three dot menu button on the toolbar on the Android device and tap Settings, there is no General item there, you need to click Customize in this menu to be able the select the Top/Bottom position.

In the instructions for moving the tool bar from the bottom to the top the instructions say: 1. Tap the menu button. Settings icon in address bar in android 2. Tap Settings. 3. Select Customize from the General section. 4. Under Toolbar, use the radio buttons to select either: Top Bottom STEP 3, There is no "Customize" under the "General" section. How can I move the toolbar to the top?

These instructions is for Firefox on Android. https://support.mozilla.org/en-US/kb/move-navigation-bar

You posted this thread in the (desktop) Firefox section so are you asking for help with Firefox on Android or Firefox on Windows, macOS, or Linux.