Zend certified PHP/Magento developer

Exception #1 (ReflectionException): Class ??ModelUiConfigProvider does not exist

I have created my own extension in magento 2.3.X
But somehow magento says all my classes does not exist.

even I registered the extension after running the setup:upgrade
As I can I see it in enabled modules.

NB: I’m new to magento but I’m following the magento docs.