Can you please tell how i find a friend of mine living in oulu. But I have lost their address.

The address of every person living officially in Finland is available in
Väestörekisterikeskus (Population Register Centre)
The telephone number is 0600 0 1000
(only in Finland)
The mailing address of Population register centre is
Kellosilta 4
PL 7
00520 HELSINKI

URL: https://vrk.fi/en/address-service