Migrate all the data from source existing server to another target existing server

Is there any steps to migrate all the data from a source existing server to another target existing server without overwriting the changes in the target server.
The changes have been done so far in target server must be there
The migrated data from source server also must be there in target server
If it is possible please help me with your information?
Then how to handle the conflicts in target server.

If you know which modules have had changes implemented, then you could export the data from those modules, and import it into the server, but otherwise it will be quite difficult to synchronise them.
The alternative is a full export of the entire system, then use a diff utility to match the data streams

@trentmu, thank you for spending your leisure time and it is quite informative.

Actually, I am doing the erpnext in docker. When I tried to migrate the sql data dumps(backup from source) to target existing server, I am getting error like this

Table ‘tabDefaultValue’ missing in the restored site. Database not installed correctly, this can due to lack of permission, or that the database name exists. Check your mysql root password, validity of the backup file or use --force to reinstall

But when I up the new dockerized frappe with that sql dumps I am able to migrate that data while initialising bench.

As per the error’s instruction I tried to reinstall the site. In order to do that I need to wipe all the existing data from my server.

you need to do a
bench migrate or bench update --reset to sync the differences in the tables between version

Okay @trentmu .Thank you, I appreciate your time.