I've never grown cukes, but for pumpkins and squash which look the same: the male flowers come first, and they have a long skinny stem connecting the flower to the vine. The female flowers start blooming a few days later, and they have a swollen stem connecting the flower to the vine.
If you have bees, then why were you told that you need to hand-pollinate? Genuinely asking, as I don't know.
