I have to admit that I don't understand anymore what is the problem in the end
Did you manage to upgrade AcyMailing on J2.5 website to the latest version, which is 5.10.24?
If yes, what is keeping you in the attempt to export AcyMailing DB tables and import them into the J4 DB?
If not, what kind of issue do you still have on J2.5 website?