Hi Sagar,
Thank you for providing the credentials. The Cart Dropdown element you mentioned can only be added in the header if you’re using Pro (see https://theme.co/docs/the-difference-between-x-pro) since you’re using X there is no possible way to add the Cart Dropdown element in the navigation menu.
However one possible solution in X is adding the element in the Topbar but that would require custom development which is regretfully out of our support scope. With that being said I can point you in the right direction.
First create a Global Block (https://theme.co/docs/global-blocks#how-to-create-a-global-block) and add a Cart Dropdown element. Copy the shortcode of the Global Block and paste it in the Topbar Content via X > Theme Option > Header > Miscellaneous > Topbar Content:
For the shortcode to work in the Topbar you need to add a code in your child theme’s functions.php file, please follow this thread: Shortcode in topbar
You’ll see the Cart Dropdown in your Topbar. Hope this helps!