Hi diogowernik,
Migration would be a good way to do it. If you are building a new user profile in SEBLOD, you can export the data from your existing users in some format. SEBLOD Exporter will work, unless you are migrating from an older version of Joomla before 2.5. In those cases you can use the export function in phpMyAdmin.
Once you have a csv file, make sure that the first row has headers (field_names).
Example: Create a Member Content Type: with extra fields such as: user_first_name, user_last_name
A user profile still needs: name, username, email, password, etc.
In the CSV file, make sure that you have all of these field names in the first row of the file and then the data. You may need to look at the field storage names to see what the names are. As cubist stated in the previous post, make sure all dates are in the yyyy/mm/dd hh:mm:ss date/time format.
Depending on the field that you are tying to import, you may have to do some manipulation of the data to get it into the correct format. This is also a good place to concatenate fields or split fields up - depending on what your profile requires.
Always remember to back up your site! Test the importing functionality on 2 or 3 records.
Hope that helps,
Randy