Hi Lata,
You're going to have to create a custom property and get your hands dirty with some Dojo.
These two blog posts should provide some inspiration:
https://world.episerver.com/blogs/Duong-Nguyen/Dates/2014/1/Country-Region-drop-down-lists-in-All-properties-mode/
https://world.episerver.com/blogs/Anders-Hattestad/Dates/2016/2/continent-country-region-drop-down-list-as-dojo-property/
How to develop cascaded dropdwonlist in episerver?