This response is TOTALLY subjective.
It depends on many more factors.
But you could evaluate
Each CRUD with only code, description
1 day
Each middle complexity USE case like input and find invoices
3 days
Each complex like some special reports where are some interaction and calculation not usual.
5 days.,
You can scan the functionality and check against it to have a brief magnitude estimation.
This is totally subjective. and many many people say they do in less than that. But if you think about programming, testing, delivering, getting feedback, testing again, checking what the customer forget to explain… a real-life example, I don’t think things last less than that.