Officially distupgrade to Debian 9 is not supported Dist-Upgrade Support
You can just install new server with Debian 9 and migrate your current server.
OH do you own the server? Well that's easy too - Get a temporary at Digital Ocean or something, where you can pay hourly. Migrate them off, wipe and reinstall your server, and the migrate them back over....
I mean... anything is going to cost you but having your server compromised for running old software/applications will cost you even more.
also i have installed plesk wit debian 9 on a new server must i migrate first in new server all my subscription from old server and must after start migration from old server?
yes i have new server with debian 9 after i need migrate this to my old server but here is no domains and subscriptions on the new server must i migrate without any subscription?