Replacing vent for stove on 2008 big country

I am needing to replace my outside vent for my stove. I am having a hard time figuring out the size I need to purchase. Wondering if anyone knows the exact size that I would need to buy.
Measure the part outside the Travel trailer, look at the part, Measure the piece of plastic, and look up online, I am replacing my stove outside vent cover and electrical outside plastic cover, I may take a picture or couple as I replace the covers on my 1987 Mallard Travel Trailer, take a couple pictures of your outside vent cover and post them here online, some one/another member will give you better information probably than I am able to give. The picture you post and the replacement parts are all very generic/parts and should be available online/big box store/or your local RV Store, good luck, Scott.