I am using Metastorm 9.1 and want to use Process events library.
There is no such thing in v9.x as you can now add and run .net code (C#) directly in the v9.x Designer.
Effectively the Visual Scripting in the Designer replaces the Process Events Library...
If you are migrating to v9 from v7, you can migrate the existing v7 Process Events library and any calls contained in pre-existing %script should still call out to the external DLL. However, I is probably just as easy to include the logic directly into the v9 BPM Solution, which should make your process deployment more simple than in v7 with the external DLL dependancy.