How to create Associated Dropdown

Hi Folks,

I have a requirement to create an associated dropdown, on the basis of State (dropdown field), region should get automatically selected.

Like there are some values in State: UP, MP, HP etc, and region is N,E,W,S, so when I choose UP, region N should get populated.

I have this question earlier as well ( but I am not able to access this link.

If any one can have access to this, kindly paste the result on this.
Many thanks!