How to move spouse's mobile number to KPN and add the number to my account?

Hello, I am an existing Internet and Mobile customer with KPN.

My husband has a Mobile subscription with Vodaphone that is ending in May. We would like to change his subscription to KPN from Vodaphone and add him to my account.

If I login to MijnKPN and click to add a product and then click SIM Only and ESIM, I’m able to proceed through the order form but I don’t see a place to enter his existing phone number so that it will port over. Do I need to do this differently?

EDIT: Okay, I see it is further in the checkout step, I just needed to continue with the order placement. You can close/ignore this question.