How the target environment is created and which permissions the Scaleway key needs is covered under Cluster provisioning. The database import and its prerequisites are described in Managed databases.
Why data should live in EU data centers of a European provider is explained in Digital sovereignty. If you are coming from a Kubernetes platform rather than straight from a hyperscaler, read Migrating from Qovery.
The route service by service, with every pitfall, is described in the article From AWS to Scaleway: what becomes of RDS, S3 and Route 53.