If you are not able to see the orde related list in opportunity then follow below steps.Elaborate your question so that I can help you further.
1.Add the Order related list to the Opportunity Layout. 2.Drag the Opportunity field to the Order Layout. 3.Profiles - Field Permissions - Orders - Opportunity (Check the Read-Edit Permission) and save.
If you are not able to see the orde related list in opportunity then follow below steps.Elaborate your question so that I can help you further.
1.Add the Order related list to the Opportunity Layout.
2.Drag the Opportunity field to the Order Layout.
3.Profiles - Field Permissions - Orders - Opportunity (Check the Read-Edit Permission) and save.
Best Regards,
Sandhya