Is my hamster a male or female?

Hi guys, I recently adopted a hamster from my local animal shelter and the employees there do not know if my hamster, Hamlet is a boy or a girl. Hamlet was a stray. Most of the time, you never see a hamster running around outside by its self. I am thinking she had an owner before and maybe she just got out? I looked online and I read people's messages about how the males have large testicle and the females don't. It can be possible if Hamlet had an owner and neutered him/her. She looks like a girl, but im not sure. I looked under her belly and I can only see one hole? From some pictures I seen all the hamsters have two? Thank you for your time, I hope I gave you guys enough information!