There are two possible answers to this question: 1. If you like, you can use "anymore" as a single word meaning "no longer" when you're talking about time. For example, "My great-grandmother doesn't go water-skiing anymore". But you can't use "anymore" where "more" is followed by a noun ( as in "There isn't any more ice cream") or refers to a noun (as in "Can I have some ice cream?" "Sorry, there isn't any more"). Seems a bit confusing? Don't worry. If you can't be bothered to get your head around that, there's always answer number 2: 2. Forget about "anymore". You never need to use it. Really.

anymore for "I don't need this anymore" any more for "do you have any more juice?"

Any more is a determiner. Anymore is an adverb. Is there any more food left? I don't go fishing anymore. anymore means any longer. Any more means indefinite quantity of something, even the smallest amount.