Can't change back to the proper world?

So i logged onto my world, and it was entirely wiped. or so it would seem. Another world is generating and i cant delete it or go back to my old world? I just want to go back to my old world. me and my friends had a lot of progress there. I've checked many threads, and they all said "Change worldname in server.properties" but theres no option for that? Is the advice outdated??

Nothing, i just started it up and it generated a new world instead of using my old one. It's still there, but i can't find a way to switch back over to it.

sp4c3yb4by.aternos.me

What??? No it hasn't, I've had it for a month or so now. the original world is mmmwrench, but for some reason it made a new world simply called "world" and i cant change back to mmmwrench. Only thing i did to it maybe two hours ago was change what it says when you add the server to your server list. "Welcome to the server of sp4c3yb4by" to "lmfao". Maybe that made it seem like its a new server?

I can't find anything called level-name in server.properties. All i see is Slots, Gamemode, Difficulty, Whitelist, Cracked, PVP, Commandblocks, Fly, Animals, Monsters, Villagers, Nether, Force Gamemode, Spawn Protection, Resource pack URL, Timezone, and Environment.

Oh, thanks! No one specified which server.properties it was in.

ITS FIXED!! TYSM!!