Stuck in a mod on adventure mode can't go from survival mode to creative

I downloaded a mod called Coty Maker i had paid 7.99 for it created the new world with it and I left the name they used I do not know if that is relevant. I selected adventure mode and created it it is now stuck in survival and the mod isn't working because I can't create.  I don't want to delete the world because I paid for it HALP. I've looked everywhere and no-one has said what worked. I don't want my money to go to waste my son was looking forward to this new mod.