These are the parts worksheets that I made and use with my orchestra beginners. This is a great activity to do during the very first orchestra rehearsal. Maybe not everyone has had a lesson yet, but you can have them open their instrument case and look at their instrument as they write the name of each part on the correct arrow line. I tried to make the diagrams look as clear as possible.
This resource includes a worksheet for violin, viola, and cello. There is also a diagram of the bow that students can label.