How do I SHOW the URL ADDRESS BAR in Safari version 14.0?

i don't know if this is what you mean.

safari preferences>Advanced tab. put a checkmark in the box.

If the address and search bar is literally missing from Safari's toolbar, then you would need to re-add it to the toolbar via:

View menu : Customize Toolbar…, click on the Address and Search tool object, and drag/drop it in the center of the Safari toolbar.