Multithreaded app for writing to a MySQL database
Yes, your code will use pooling.

You might, for the sake of server efficiency, use a smaller MinimumPoolSize (say, 20), and a larger MaximumPoolSize (something a little larger than your maximum number of threads).

You probably don't need all those connections all the time.  If your threads do anything significant between their uses of the function you've shown, a significant number of your connections will be idle.

Unless you're sure you need all those connections all the time, you should reduce the RAM and thread burden on your server with a smaller MinimumPoolSize.