Hi @IslamElkhouly,
The impact varies by release. Before upgrading, extract the updated WEB-INF/config and compare upgradeObjects.xml and its referenced files with your current version to determine which workflows, rules, and forms the upgrade will re-import.
As @santhirajumunganda suggested, take back up of all custom objects. Reimport after the upgrade.
Store copies in source control and deploy them through SSB/SSD to ensure consistent post-upgrade deployment