Write SQL query to solve given problem: How many sales does game platform id 3871 make in Europe?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.num_sales * 100000 FROM region AS T1 INNER JOIN region_sales AS T2 ON T1.id = T2.region_id WHERE T1.region_name = 'Europe' AND T2.game_platform_id = 3871