Nothing Showing Properly!

when i opened unity today everything but my plane object was showing and the color of the object was pink. I checked the hierarchy and there were a lot of objects saying missing prefab. I checked the game folder and everything seemed to be right. There was no missing asset but in the project menu there were a lot of assets missing which were there in the folder. Please help otherwise hours of work will be lost. THANKS A LOT IN ADVANCE!