Returning visitors and Import log

Hi,

With last version of Matomo self hosted, i import log every days for have stats.
But i haven’t returning visitor, i don"t anonymise Ip for have returning visitor identification.

It is possible to recongnize returning visitor with Ip and user agent or other ?
After 1 month i anonymize data for privacy but i want returning visitor is identified with import logs.

It is possible to do it ?

Thanks

I have finded this :

How to have re calculate returning visitors ?