Studios do change engines from time to time, but it usually involves a lot of work and lots of custom pipelines.
If the project is small enough it might be better to just start from scratch. UE and Unity are fairly different.
If you still find that you need to port things over, you could look into automating exports from UE using Python. I believe (somebody correct me if I’m wrong) Unity does not have a de facto workflow automation framework, so you way have to look into 3rd party solutions for the import side of the pipeline.