I have erpnext version v6.27.15 How do I update to 7
ERPNext 7 is not officially released. But you can try it by using the develop branch (for Frappe and ERPNext), where it’s still being worked on. I would not suggest changing your production site to ERPNext 7 as of right now.
You can either create a new frappe-bench
or you can download the VM, switch the bench-repo to develop and then do bench switch-to-develop
followed by bench update
You can also setup a VPS on say, DigitalOcean and run the Beta Development script