Hey @Chaewon_Lim! Welcome to the community and thanks for reaching out. 
This is definitely a challenging problem - we have an internal utility for handling the opposite scenario, but I'm not aware of anything to specifically help migration from on-prem to Cloud. 
That said, I think there's probably a solution to the UUID issue that you're seeing. In theory, you should be able to write a script that POSTs app JSON files - not ZIP - to /api/pages/createPage, starting with any shared modules. The important thing about this endpoint is the fact that it attempts to match modules by both UUID and name.
If you're interested in talking through this solution or even working on a proof of concept together, feel free to join our scheduled Office Hours!