Welcome to the community, @Jen_Gordon!
MID( Attachments, FIND("(",Attachments)+1, LEN(Attachments)-FIND("(", Attachments)-1 )
There might be other ways of doing this as well!
Hope this helps! If this answers your question, could you please mark this comment as the solution to your question? This will help other people who have a similar question. :slightly_smiling_face: