I would start here:

https://docs.automationanywhere.com/bundle/enterprise-v2019/page/enterprise-cloud/topics/deployment-planning/on-prem-install/update-enterprise-a2019.html

If you have further questions, I might start a support ticket or consider contacting our professional services group for assistance.

Thank you so much for sharing the document and for your response. 

We have four Dev servers. On one server, AA360 application is hosted and two servers are using for Development and one server is for bot runner machine. could you please let us know from which server do we need to take backup from.

Hi,

For the upgrade, you’ll want to back up the Control Room server, especially the database with all your configurations and settings. Make sure to save your license info too, just in case. For the development servers, back up the bots and any custom files you're working on.  If you’re unsure or need extra help, it’s worth reaching out to Automation Anywhere support.

Hope that helps!

Thank you for your valuable response.