You can't tell what you have until they bloom. Male papaya plants have panicles (long stems) with many small fragrant flowers on them. Female papayas have larger single flowers close to the stem of the plant. If you have male and female plants in your garden they will pollinate but you will get fruit only from the female plants.
But sometimes they have both kinds of flowers or "complete" flowers that will self-pollinate and then you don't need both kinds. In places where they grow papayas commercially, they remove any that are not "complete" also known as hermaphrodites and only keep the self-pollinating plants because then you will get fruit from every plant.
If you start your papayas from the seeds of one that was commercially grown, the chances are pretty good you will get some self-pollinating plants.
