Update my php codeigniter version 2 to version 4

I am looking for a skilled developer to update my current php codeigniter version 2 to version 4. The project is for an existing business and there are a few customizations/extensions that need to be taken into consideration. In addition to the upgrade, I also require some additional features/improvements to be added. The ideal candidate should have experience with php codeigniter and be able to efficiently complete the upgrade while ensuring all customizations are preserved. They should also possess strong problem-solving skills and be able to implement the requested features/improvements. My budget is 500 usd and milestone will be paid for each milestone addressed.