Hi Skye,
Welcome to KittyCatS !
Never dumb questions here.
1 - To get a cat or box back from the Cattery, you need a 'dock', available for free in the lobby at the main store.
(Rez the dock, left click it, then click on "Cat to SL")
2 - To add more K$ to the Cattery, you can either purchase some via the dock or buy a gift card at the main shop.
We can't transfer the inworld food into the Cattery or vice versa.
3 - If you breed your cats inworld, you will get the box inworld (along with a message of the mum telling you she had a kitten and a link to the box), if you breed them in the Cattery, the box will be there (you can sort boxes by date of birth).
Have fun breeding !
Nen