Lost all my worlds, servers, and can't use mods.

I lost all my worlds and I can't use any of my old resource packs or mods I have downloaded. I can infact open my mod folder but when i use forge (which I also had to re-download -  [1.12.2] ) It starts but doesn't include any of the mods that worked perfectly fine before. I don't have much friends to play minecraft with and I really enjoy playing modded minecraft on singleplayer worlds, which I can't at the moment so I really, really, beg for your help or input on how I can fix this. Thank you.