Create Field SELECT in Checkout Woocommerce

I'm using Woocommerce along with the WooCommerce Extra Checkout Fields for Brazil plugin.

I need to have additional fields, but with conditionals, both fields will be SELECT , where the second field would only appear with a certain option if the answer of the first one is X . For example:

Stores in SP: Then the second field of the select opens with the options of the only store of SP; Stores in RJ: Then the second field opens only with the stores of RJ.

Would anyone help me with the best way to create it?