How do I move clock to the right end of GNOME 3 Panel from the middle?

You may use a GNOME shell extension called Frippery Move Clock to achieve this goal.

Also another extension called Unite

[...] makes a few layout tweaks to the top panel and removes window decorations to make it look like Ubuntu Unity Shell.

Moving the clock to the right is among the modifications it does.

Here is how I did it (on Ubuntu 18.04 LTS):

1. Launch 'Ubuntu Software' which is built in Ubuntu 18.04.
2. Install 'Dash to Panel' shell extension from 'Add-ons' -> 'Shell Extensions'. Scroll down to find the 'Dash to Panel' extension and install it.
3. Press 'Extension Settings', find the settings button of the 'Dash to Panel' in the menu.
4. Open the configuration settings of 'Dash to Panel' and find the 'Position and Style' tab. On this tab you would find the 'Clock Location' configuration. Change this to 'Right of status menu'.

This would work. However, the side-effect (desired effect in my case) is that the 'Top panel' and the default Ubuntu 'dock' would merge together to form a single panel just like in the Windows OS.

You can use the Extend Panel Menu which is found at https://extensions.gnome.org/extension/1201/extend-panel-menu/