The cat farm is a location in Dondoruma City used to obtain extra items. You may only choose one of the options between each quest initially. To upgrade your farm to receive better items, you need stamps from buying furniture from Mezeporuta Square. You can also temporarily upgrade your farm by buying garden supplies such as special picks and watering cans from him that can be used a few times before needing to buy more (you can check how many times you have left by reading the sign in the cat farm). Whether you want to upgrade your farm with stamps or buy gardening supplies, you need to visit the furniture man. Check the furniture link for more information.
You may also receive free items from the cats that wander around the farm, such as mega bugnets, trap tools, and tranq bombs.