Ask the vet - Rabbit
How is the gender of a baby rabbit (kit) determined?
Vet at FirstVet answers:
It can be very difficult to see what gender a baby rabbit has.
Females have an opening that looks like a straight slit while the males’ opening is more circular. It will help if you have several rabbits present to compare to.
You can search for photographs online and compare them to your kit.
If you still find it difficult it is best to consult a veterinarian or potentially a knowledgeable pet store staff member.