How should I ask her for her number?

Hey! So this cashier I see almost everyday works at the gas station just down the street from my work. One day when a different cashier was up cashing me out, she ran up there behind him, and asked me my name. I told her my name, and she told me hers, then quickly dashed away.

I think she is interested in me, and I’ve been unsure how to approach her for her number. We spoke a few once since, and she mumbled my name wishing me a nice day, and looking up all shy like.

My question is, how could I approach her for her number? I don’t want to be awkward and assume she's wrongly interested, thus making every stop there awkward. Thank you in advance!
How should I ask her for her number?
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