I see. Let's think this through step by step...
Even though your Fabric API file and Wurst Client are in the
curseforge\minecraft\Instances\jespin\mods directory, the Fabric Loader isn't detecting your Fabric API.
Based on that path, I'd assume that you're using the CurseForge/Overwolf app as your Minecraft launcher (if not, that could be a problem). I can also see that your system opens these files with Internet Explorer by default, which is a bit unusual but not necessarily problematic.
As a first troubleshooting step, I'd suggest you to check the file extensions to make sure both of these files actually have the
.jar extension. Fabric Loader recognizes only
.jar files as mods, and some launchers may "disable" mods by renaming them to
.jar.disabled. This would not be visible in your above screenshot and could be the root of the issue.
Secondly, verify that your Minecraft launcher points to
curseforge\minecraft\Instances\jespin when launching Wurst. If it doesn't, it might be using a different mods folder that doesn't contain the Fabric API. I'm afraid I can't give you specific instructions on how to do this, as I don't use the CurseForge/Overwolf app myself.
Good luck and let me know how it goes!