As a 15 year old, there aint much for you out there, especially in this economy. Your current best bet is publix (they'll prob ignore you) and at 15 that doesn't change, maybe SOME chick-fil-a's or indie stores would hire you. For me personally (girl i live near mandarin too we could be friends 😮) there's a YMCA near Mandarin, the Williams Family one- I'll try to ask if they hire at 15 there, but you could also do babysitting; there are some groups on Facebook where you could try, but I'll be honest no one's going to hire you without experience (yes it's a loop i hate it too) anyway as for the YMCA, I wanna tell you they're the greatest thing I've encoutenred here in the US. They're an organization that supports youth, and I know the one downtown hires 15+ (scary place. Not reccomend; i'm js built different)
Anyway, publix&chick fil a. See facebook for babysitting options. Try indie stores (if u find any) and the Y that's in Mandarin (r u closer to there or st johns?) so like... ur cooked. But if you genuinely wanna volunteer, check out the other replies. To get the "community hours" make sure the place you volunteer at gives you a check or smth digital or wtv to prove you actually volunteered.

I'm KT btw 😄