What clothes and other items should I bring to Suzhou for internship in March this year?

First of all, congratulations on finding an internship in Kunshan.

March belongs to early spring, and the spring is chilly. You don't need to bring a down jacket, you can bring some coats that are slightly thinner than the down jacket. In March, almost a sweater and a thin cotton-padded jacket will do. It's going to be hot in April, so a thin sweater and a sportswear will do (sometimes I just wear a slightly thicker long sleeve and a sportswear).

The weather will not be lower than 10 degrees after March.

You don't need to bring daily necessities, just buy some in the local supermarket, which is nothing more than toothpaste and towels.

As a fresh graduate, I wish you a happy internship.