Hi darling,
In Russian we say голубцы из молодой капусты, not голибцы.
The adjective is молодой beacuse we talk about the cabbage, and in Russian this is feminin, singular.
The adjective молодые is plural. So we can say about голубцы like this becasue it is plural.
молодые голубцы
But in this case we make a cabbage rolls from the young cabbage.
Nominative case will be молодая капуста , but here we use genitive case taht is why the ending is different молодой капусты. The same about томатная паста (feminine, singular, nominative case), but in genitive - томатной пасты.
I hope it helped