"Her father sells bento at the convenience store."
That's also correct! It's apparently more common to put the direct object closer to the verb, but you don't have to.
an お infront of a thing is just used to be more polite, or to elevate the thing to a higher standard. hard to describe imo xD
I swapped the "her father" part and the "at the convenience store" part in my answer and was marked wrong. Is that actually wrong?