@RamprasadK1713 This is a very broad topic and needs lot of research and patience. 

What i understand is that you will be not using Pega Cloud , but moving to your customer provisioned  AWS Cloud. 

I would say that, focus on the following points:

1. Identify all the PRPC frameworks in scope. Framework upgrade always gets a bit complex.  Prepare a matrix of all the required versions and get their installation guides. 

2. Look at all the external integrations you have across the platform. This will give you a good assessment on networking and security requirements. 

3. Assess the size of your Database. On-prem to cloud migration needs proper data migration strategy. 

4. Look at the amount of UI customization done. This can eat away lot of your upgrade efforts. 

5. Understand the migration tools available from AWS. 

There are lot more things to do, but you can start here. Hope this helps.