These are exercises I created for you on MusicTheory.net:
Beginner Violin 4th Grade/2nd Year Violin 5th Grade/3rd Year Violin
Beginner Viola 4th Grade/2nd Year Viola 5th Grade/3rd Year Viola
Beginner Cello and Bass 4th Grade/2nd Year Cello 5th Grade/3rd Year Cello
4th Grade/2nd Year Bass 5th Grade/3rd Year Bass