I am running a stellar-core private network with version v10. Now I need to upgrade it from v10 to v12. I have gone through the stellar documentation but did not get any steps. One more thing I would like to share, I am running horizon with version 16 for stellar-core 10 and its internal database which has 11 tables. As per my research for version 12 we need horizon 20 or more than that. But for horizon version 20, its internal database has 16 tables. In this situation how could upgrade my whole network.