How do i know if my H1B petition was filed with COS or not?

How do i know if my H1B petition was filed with COS or not? I just have case number approved which states “Your I129 petition has been approved”? What does it say in case of H1B with COS ? Or if not can i file COS now ? Thanks.

Look at the approval notice i.e. 797A or 797B. If it has an I-94 attached to the bottom of it, then COS has been approved.