Hello Campbell, and welcome to the forums.
Not quite sure what you mean by "requirements at credit level Grade 3". Are you after a copy of the Grade 3 syllabus? You haven't specified which instrument (the requirements are different for each instrument), so have a look at
the syllabus page and download it from there.
If you just want more information about what's expected at Grade 3, have a read of
These Music Exams, an AB publication which explains all about the exam process.