Explanation
You can use the Microsoft SharePoint Migration Tool to migrate files from a file server to SharePoint Online.
The Microsoft SharePoint Migration Tool has a number of filters you can use to define which files will be migrated. One filter setting is "Migrate files modified after". This setting will only migrate files modified after the selected date.
The first phase of a migration is to perform a scan of the source files to create a manifest of the files that will be migrated. You can use this manifest to identify all the files in Share1 that were modified or created during the last 90 days.
References:
https://docs.microsoft.com/en-us/sharepointmigration/spmt-settings