When I try to open my 1.13.1 map, it crashes while loading the world. I assume there is a compatibility issue since the only forge installer I could find was 1.12.1, but I don't know how to fix it. It asked me to convert the world when I tried to open it. Everything seemed fine but it just crashes every time. I've tried searching the issue. One suggestion was to delete the options.txt file. That did not work. There was also a suggestion to delete optifine. I don't think I ever downloaded it but I found a couple of folders in my skin pack labelled optifine. I deleted those.
To clarify, I can open a new world and run it just fine. However, I'd like to use the world I've been working on for the last few weeks. Is it possible to convert it?
My apologies I'm a noob to Forge and mods.