I would ask why you are doing that? Is it cost reasons? Have you looked at Gen2 capacity? There are going to be some capabilities that are not available in PBI RS and there is no guarantee features on the service will be put on PBI RS. Just food for thought since MSFT has made it clear that most of the investment will be on the service and not PBI RS moving forward.
yes it is because of cost reasons and in my oragnisation they are using PBI RS but i have created report in PBI service earlier. now we want that report is accessible by everyone so we are planning to move to RS pbi.
Sorry, If it doesn't work, I'm afraid it can't be migrated, because service and report server are completely separate things. Although it's hard to accept, You need to recreate the report in RS desktop.
You can also sumbit your idea to help us improve PBI and maybe it will come in the future.
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.