Okay sorry, new direction 
So, first of all, delete the new on-premise installation first:
docker-compose down --remove-orphans --rmi local -v
docker volume rm sentry-clickhouse
docker volume rm sentry-data
docker volume rm sentry-postgres
docker volume rm sentry-redis
docker volume rm sentry-kafka
docker volume rm sentry-zookeeper
docker volume rm sentry-symbolicator
This should remove everything the onpremise repo created, including its data.
Now you need to do:
docker inspect sentry-redis
docker inspect sentry-postgres
docker inspect my-sentry
To find which volume is used by which container. Note the output of these docker inspect calls as now we’ll use them to rename these unnamed volumes.
First, create the named, empty volumes:
docker volume create sentry-data
docker volume create sentry-postgres
docker volume create sentry-redis
Then copy from the old unnamed to new, named volumes:
docker run --rm -v <volume_name_used_by_sentry-postgres>:/from -v sentry-postgres:/to alpine ash -c "cd /from ; cp -av . /to"
docker run --rm -v <volume_name_used_by_sentry-redis>:/from -v sentry-redis:/to alpine ash -c "cd /from ; cp -av . /to"
docker run --rm -v <volume_name_used_by_my-sentry>:/from -v sentry-data:/to alpine ash -c "cd /from ; cp -av . /to"
Once this is done, when you run ./install.sh it should now take your old data and upgrade it. If this works well, you can then delete all the old stuff (the my-sentry, sentry-postgres containers etc. and all associated unnamed volumes).
Hope this helps.