We need to migrate/sync almost all entities like workflows, projects, board, screen, custom fields et., between two Jira cloud instances. We have tried all the possibilities to do so. Is there any chance we can achieve that using Jenkins.
Please suggest if any…
Hi,
Better late then never 
Yes you could, it would require a lot of work to use the REST APIs to extract the entities from one instance and then create/update the entities in another instance.
If its a one time thing, then this could be good starting place.
But if you are keen on keeping the two Jira instances in-sync, then a Jira app (most likely a connect app) would be a better approach.
Cheers,
Mark