How to convince my parents?

how can i convince my parents to let me go to an anime convention. i am 13 and completely responsible but that isnt the problem. i have already asked my parents if i could go to one and after i asked her and told her the two closest ones were in dallas TX and austin TX. she said no because my mom is not a fan of going to dallas and austin is a little too far away. it took me three days to build up the courage to ask her that and after she said no my, courage took a nose dive. my dad wasn't part of the conversation so he didnt get a say (sadly). but i didnt even get to finish my argument (well it wasnt much of one). and neither of my parents know what cosplay is so thats a problem. but anyway, how can i convince my parents to let me go even after all that????? BTW sorry for the rambling but this is REALLY important to me!