Hi there, @aarti… the article in this post is old, but the concept of how to constrain a dropdown by another dropdown’s selection is still relevant.
If you are using option sets to define your dropdown options, you would add an attribute to the second option set that links each option to an option in the first option set (or you could add an attribute to the first option set that holds a list of options from the second option set that are associated with each option in the first option set). Then, in the second dropdown, you would get all of the options and filter them to those that are associated with the option selected in the first dropdown.
Hope this helps.
Best…
Mike