Jean,
the parallel port is a long one, with about 25 holes/pins in 2 rows of 13 & 12. (Sometimes called a longer serial port, also known as DB-25, and RS-232)
The serial port is a shorter one - 9 holes or pins, in 2 rows of 5 & 4.
If there is short blue one with 3 rows, it'll be the VGA graphics...