Hi Nargis,
As mentioned, if you intend to use SAP screens / SAP GUI screen, then that can be added with some configuration in SAP system. Check the link I had given in my earlier response.
If you want to change the Sales order from Fiori app, then you will need configuration(SD functional consultant), change in Fiori screen (UI5 Developer), change in backend gateway service (ABAP developer).
Hope this helps, one request will be mark answers helpful/ correct so that it helps other people in future who search the same topic.
Regards
Rishab