How do I ask for a girls phone number without sounding like a creep?

So there’s this girl that works at a gas station that I’m really into, and I’m prettyyyy positive that she’s into me to but the only problem is that now every time I see her my brain shuts off and I don't know what to say. Can someone please give me advice on how to get over the dead brain and ask her?
How do I ask for a girls phone number without sounding like a creep?
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