What kind of food will help my cat gain weight?

I'm not sure about any wet food, sorry. I do however know that Whiskas cat/kitten milk is really good for them and they love the taste, so maybe pour it over her wet food? I feed my kitten and my 1 year old the milk poured over their Fancy Feast canned, and the baby is growing like a weed!! I hope I helped, good luck!!