How do I configure multiple routing ports while migrating from CLB to ALB?

I understand that you have multiple listeners for your CLB. While using migration using console, If the Classic Load Balancer has multiple listeners, the wizard uses the listener port with the lowest value for the target group port. Each instance registered with these listeners is registered with the target group on the listener ports for all the listeners

This is why you are seeing just one target group for your two backend port.

https://docs.aws.amazon.com/elasticloadbalancing/latest/userguide/migrate-classic-load-balancer.html#migration-wizard

Is there a way to set two routing ports during migration? You can use the Option 2, https://docs.aws.amazon.com/elasticloadbalancing/latest/userguide/migrate-classic-load-balancer.html#load-balancer-copy-utility which should create two target groups for each of the listener backend port considering you are using different backend ports for the CLB listeners.