My name is sierra and I'm 10.I need a job,fast.I tried to get a dog walking job but no one would hire me.all I need is a job and I'm happy.

Clean your room or help your parents with chores... after you do your homeowrk.. thats all you are going to have time for anyway.

You could do chores in exchange for allowance money from your parents, it's basically the same thing as working elsewhere. I know it's nice to get out of the house and away from your parents now and then but go for a walk instead of going out to work... enjoy how much time you have to not work at a job right now in your life.
Another idea, if you really need to work:
You could offer to do yardwork like weeding or taking out garbage/sorting recycling for people in your neighbourhood if your parents are okay with that?
When I was about 10 I used to rake the next door neighbours yard for unlimited access to their trampoline... Pretty damn good deal if you ask me haha

P.S. I saw a few weeks ago a pink paper at a bus stop that said "Sierra and Brianna's(?) Dogwalking"
Was that miraculously somehow your poster? If so the internet is smaller than I thought and that is a weird happenstance...
Also if that was your poster, it got really wet in the rain and letters ran, people can't read it! It's not a bad idea putting out posters... Just use paper that can resist moisture a bit better for next time :P

OMG your TEN am 14 an am not looking for a job when I was 10 I was out playing with mates you can't get one at 10