How can I ask this girl out or get her number in two minutes or less? Is it even possible. I don't know her and seen her once only.?

Okay so I am in a small town, I'm not from here but I'm staying at this place for a week. Upon arriving to this town I had to help my dad get the groceries. By the way he lives here and I'm here helping him out for abit. But will be leaving in a week. So anyway as we approached the checkout I seen this girl working on the checkouts across from us, as soon as I looked at her she looked up and we looked at eachother for like a second not knowing what to do I smiled and she did the same. So I'm not a weird person or anything but this girl is pretty and I'd like to hang out with her for abit. But how should I approach her again, what can I say in like two minutes or less that can make her interested in me or at least get us to meet up at another time in the city (small city) I don't know how old she is though I'm 18 just finished school last year. When back in school this stuff was so much easier but now... So yeah any help guys. I'd be so grateful for some responses. Sorry for such a long post