To find out how many of DJ's movies are comedies, you can use the fraction given: \( \frac{3}{8} \) of his 16 movies.
First, multiply the total number of movies by the fraction of movies that are comedies:
\[ \text{Number of comedies} = \frac{3}{8} \times 16 \]
Now, perform the multiplication:
\[ \frac{3 \times 16}{8} \]
Calculating the numerator:
\[ 3 \times 16 = 48 \]
Now divide by the denominator:
\[ \frac{48}{8} = 6 \]
Thus, the number of comedies in DJ's collection is \( \boxed{6} \).