WorldPreview requires Java 16+ and Fabric 0.12.2+ to work. You can install the latest version of Java here https://adoptium.net/temurin/releases/ (install the .msi file if you're on Windows) To get Minecraft to use that version of Java,

• on MultiMC: Go to Settings > Java > Auto-detect and select the latest version you have.
• on the official Minecraft launcher: Go to Installations > "..." for the installation you're using > Edit > More options, click the "Browse" button for Java executable and navigate to C: > Program Files > Eclipse Adoptium > jdk-x.x.x.x > bin > javaw.exe. Select the javaw.exe file. You will then need to delete JavaCheck.jar. If Minecraft still crashes with Unsupported mixin class version 60, update Fabric Loader.

i stole this from the discord whcih is a better place to ask these questions