Export only a part of the database for migration

If you don’t mind exporting pages and posts separately, you can use the default WordPress export tool to achieve that.

On the Export screen you can set the tool to export only posts. Then add a suitable date filter. After that do another export, but this time set the tool to export only pages.

You can read more about the default export tool on the codex, https://codex.wordpress.org/Tools_Export_Screen

I think majority of the backup/export plugins only let you choose which database tables are backedup/exported instead of letting you do such conditional/partial export.