How can I reach from Bangalore, India to Taizhou by flight

You need to fly to HK first and then fly to Shanghai.
Then from Shanghai, you need to take a bullet trains for Taizhou.

I want to reach " Chumen Town, Yuhuan County " , which is the nearest international airport to this? exact destination "Yuhuan County Hongda Sanitary Ware Manufacturing Factory"

According to the distance, the Wenzhou International Airport is the closest airport.
I helped you to check and found that from HK there are flights to Wenzhou, so you can take this flight.
Upon reaching Wenzhou airport, you can take the airport shuttle bus to reach city proper and then change a taxi to Wenzhou Xinchengzhan Bus Station (新城站汽车站), where you can find the direct buses for the Yuhuan county.
I just know the factory is located in Qianpai Industry Area, but no other information can be known, I am afraid.

Hope these information is helpful.