Make 'Project number' data field as mandatory on purchase order via sandbox

Summary

Project number field not available to make it mandatory on purchase order via sandbox

Content

Hi,

Our requirement is to make the project number field mandatory when creating a purchase order. I have created a new sandbox and added a page composer tool under it and activated too. However, when I edit the properties of the project details section, I do not find the project number component to make it mandatory. See the attached screenshots.

Has anybody tried this earlier? Thanks for your help.

Thanks/Amit