I'd be more than happy to convert them for you! Give me a couple days (after going to school, working for my grandma, and homework, I don't have that much time on my laptop, lawl) and I should have them all done.
EDIT: The Ocotillo plant and the tree appear to be really high poly, so they will be horrible laggy in the game. I can probably find you some better savannah-y plants if you'd like?