Upgrade your postgreSQL Database from 14 to 15 on Debian

I wonder how I can upgrade the data from an existing PostgreSQL 14 installation to 15. I automatically got PG 15 installed via apt, so I see # dpkg -l | grep ii | cut -d" " -f3 | grep postgresql-1 postgresql-14 postgresql-15 But the data is still all in PG 14. There are two services service postgresql@14-main status and service postgresql@15-main status