help me plss

Okay so this is probably really common and easy to fix but I've been at it for six hours using THREE DIFFERENT AI bots and i cannot for the life of me figure out what's wrong. Basically, every time I upload the mod which is currently just a content.json, a manifest.json, and an assets folder...

I have been really wanting to make a Stardew valley oc board but the website won't let me! Will someone make it for me, I can give you all the photos and info. Priv message me please!!!!!!!