Is there an apostrophe on friends?

It depends on the context in which you are using the Word.

If you are simply referring to more than one friend (i.e. a plural noun) then there is no apostrophe.
For example: I am going to the cinema with my friends tomorrow.

If you are referring to one or more objects belonging to one friend then you use an apostrophe like so: friend's.
For example: I borrowed my friend's textbook to do my homework.

If you are referring to one or more objects belonging to several friends then you use an apostrophe like so: friends'.
For example: My friends' dresses arrived in store a week before prom.