Newbie: it appears tank hoses don't come with new trailer

Walmart has 50->30 adapters for ~$7 and 30->50 for ~$9, whichever you need I suggest buying a couple. I have a good Camco dogbone that I forgot at home, $7 would have saved me an hour round trip last night to the nearest Walmart. The Walmart ones are a lot smaller than a dogbone so you can just toss them in your spare parts/tool bucket.