I reinstalled fabric to get 1.16 (I was using 1.14) and modmenu now doesn't work.

These are my current mods:

When I launch, it crashes with that error message and I can't play.

So you need to install fabric-api itself. resource-loader is a completely different mod.

So you need to install fabric-api itself. resource-loader is a completely different mod.

sorry for the delay; I already have fabric api. It's in the screenshot

Do you still have this issue in 1.16.2 with latest fabric api ? (0.19)
and also worldedit-forge ...
and I'm not used to windows 7; are the mods folder ?

Closing due to lack of feedback. If you need further assistance, please join the Fabric discord https://discord.gg/v6v4pMv