Do a google image search for 'sex marijuana' and itl bring up many pictures.
The most you can expect to see on those plants will be pre flowers, which will be two hairs pointing upwards for a female, and a pair of small circular sacks (usually hanging down) for a male. Although if the plants are vegging they may not have pre flowers.
Im currently 2 weeks into my first grow, got 3 auto ak-47's (the auto flower element means they show sex earlier) and two of them have just shown sex. Was rather unsure what I was looking for, but trust me, you'l know when you see it.