Currently we are using Sitecore 8.2 Update 3 and planning for sitecore 9.1 Update-1 upgrade.
We have following set up currently:
1 CM server
5 CD server
Can any one suggest best approach to upgrade the below things from sitecore 8.2 update 3 to 9.1 update 1.
1) Core DB Items (including custom tables)
2) Master DB Items