This guideline will help you transfer historical data from your Branch integration to Remerge.
Remerge requires one csv file per OS in this format:
android_file.csv
device_id, timestamp
The max(timestamp) will be enough. Usually we receive one file for app launches and another file for past purchases.
Please view here how to do csv file exports from Branch:
https://branch.dashboard.branch.io/data-import-export/csv-exports