Getting value of dataset from dropdown

HI,

I have a dropdown that shows one field from a collection using a dataset. How can I get the others data from a data set when a choose a row in my dropdown?

Example:
My Collection: Field A, Field B, etc

Dropdown: Showing only Field A.

When I click in a button, I want to get the value of is selected in the dropdown and the value of the field B that is related to Field A.

Have a look at this tutorial from Nayeli (Code Queen):
https://www.youtube.com/watch?v=EhXed0u6wh0
https://www.wix.com/corvid/reference/$w.Dropdown.html