The total count of elements in a matrix is the result of multiplying its row count by its column count:
\[m \times n = 36,\]
where \( m \) represents the number of rows and \( n \) represents the number of columns.
To identify the matrix's potential dimensions, list all pairs of positive integers \( (m, n) \) whose product is \( 36 \). These pairs are the factors of \( 36 \):
\[(1, 36), (2, 18), (3, 12), (4, 9), (6, 6), (9, 4), (12, 3), (18, 2), (36, 1).\]
There are \( 9 \) such pairs, indicating \( 9 \) distinct matrix dimensions. Therefore, the number of possible dimensions is (D) 9.