If enemy go to battlefield A where I have unit, I use Ride the Wind to other battlefield. Which one score first?

To address your question regarding the showdown sequence and who scores, we must look at the impact of moving your unit away from a contested battlefield while a showdown is in progress.

The Ruling

If your opponent moves a unit to your battlefield (Battlefield A), initiating a showdown, and you use Ride the Wind to move your unit to a different battlefield (Battlefield B), you do not score at Battlefield A. By moving your only unit away, you leave the opponent as the only player with units at Battlefield A. Consequently, your opponent will establish control of Battlefield A and conquer it, potentially scoring a point if they have not already scored it this turn (Rules 461.5.d, 461.3.b).

Sequence of Events

Following the <showdown_flow> and the provided <retrieved_context>:

1. Initial Contestation: Your opponent moves a unit to Battlefield A, where you have a unit. This triggers a showdown. You are currently the defender.
2. Playing Ride the Wind: Assuming you have priority (or the state allows), you play Ride the Wind. This is an [Action] card that uses the chain.
3. Resolution of Ride the Wind: Your unit moves to Battlefield B.
   • Note: If Battlefield B was empty, this movement immediately initiates a "Non-Combat Showdown" at Battlefield B, which becomes "staged" (pending) while the combat at Battlefield A continues (FAQ #9976).
4. Battlefield A Cleanup (Step 3 of Showdown): With your unit now gone from Battlefield A, the combat cleanup occurs.
   • Per Rule 461.3.b, you lose the combat at Battlefield A because you are the only player who does not have units remaining at this battlefield.
   • Per Rule 461.5, since your opponent has units remaining and you do not, your opponent establishes control of Battlefield A.
   • Per Rule 461.5.d, this results in a conquer for your opponent, allowing them to score a point if they haven't already scored Battlefield A this turn.
5. Staged Showdown: Once the showdown at Battlefield A is completely resolved (including combat cleanup), the "staged" showdown at Battlefield B begins (FAQ #2099, FAQ #9976).

Summary

You do not score at Battlefield A because you abandoned it during the showdown. Your opponent wins that combat and conquers the battlefield. The showdown at Battlefield B will only be resolved after the combat at Battlefield A concludes.

Disclaimer: This is my interpretation based on Rule 461 and the relevant FAQs (notably #3278 and #9976). No official FAQ exists for this exact scenario, but this aligns with established combat resolution mechanics.