Thank's for answer Till,
i have copied all mail's files in the same folder.
For example in ISPConfig 2 the folder for mail was:
/var/www/www.domain.tld/user/mailname/ and here i get 3 folders
cur new tmp
In ISPConfig 3 folder for mail is:
and here i have the same 3 folders cur new tmp.
I copied from new to new, and then when i check with thunderbird client i get some errors