The calm Hopper was exuding was a lie. He was a wreck on the inside. But he had the presence of mind to keep that from showing outwardly. He didn't really know what was going on, but he didn't want to upset Steve. So he stuffed the urge to freak out down, and kept a cool, calm appearance.
Never let them see you sweat, or something along those lines.
"Drinks first. Clothes second." And he was going to have to see about getting some Eggos. Even if El wasn't here, he wanted to have some in the freezer. Assuming he had a place to sleep. Assuming that place had a freezer. He'd deal with that later. Drinks were priority one. Honestly, his priorities were drinks, smokes, Eggos, find a place to sleep, clothes. He really didn't care all that much about the clothes.
"I don't know. I was ready, I knew what was going to happen. Figured it would be over in a matter of seconds. But then I was here. I don't know how. I don't know why, unless it's all in my head. Some kind of death dream." But why Steve? Steve Harrington was one of the last people he'd expect to imagine by his side at the very end of everything.