Hi Marilia,
You have 2 options to perform this migration
Option 1: Using the same server
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1) Perform the SAP database export of source system
2) Scrap the source system
3) Prepare target system
4) Install target system
5) Perform import into target system
6) Perform post migration steps
Option 1: Using different target server
==========================
1) Perform the SAP database export of source system
2) Prepare target system
3) Install target system
4) Perform import into target system
5) Perform post migration steps
I shall suggest Option 2 , as you will need source system for some time inorder to have a fallback scenario and perform data validation before and post migration.
Hope this helps.
Regards,
Deepak Kori