Hi Vkas,
The page is classic page, not in the power apps.
You can go this page as following step:
1.Go to Entities and click on the gear icon and select Advanced Settings and it opens the classic settings menu in Dynamics.

2.Expand Settings and click customization > customize the system > Entities.

3.Then you can see above screenshot, you can expand Entities to select one and see its field list.
Regards,
Leah Ju
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