Can you suggest a good online course to learn ArcGIS Enterprise? How much does the software cost?I would like to go for a certification later.
Here is a good place to start for training: www.esri.com/training/Bookmark/PKH3TBEWR
Here is information on the exam: https://www.esri.com/training/catalog/5ba127e646fee07da2714e7c/enterprise-administration-professional-19-001/ and preparing for the exam: https://www.esri.com/training/catalog/5dcb0c43e5aa0452316eb995/preparing-for-esri-technical-certification/
Esri Training Esri Technical Certification
If you are starting out from scratch with ArcGIS Enterprise, which it seems you are, it will be a sizeable time and financial commitment to get certified in ArcGIS Enterprise. If you don't work for a company/organization that already has access to ArcGIS Enterprise licensing, then an ArcGIS for Developers subscription is probably the least expensive way to get access to all of the various components that make up ArcGIS Enterprise. That said, the minimum Developer plan that includes ArcGIS Enterprise is Professional at $1,800/yr.
In addition to what George and Joshua posted, please see my comments in your other similar topic thread where I've reference some video links you can watch
Hope this helps,
Retrieving data ...