Google Workspace / Square Space Google domain

I have been using Google Workspace since 2018, set up via Square Space, (my company website in hosted on square space). Last year I changed my website from www.beyondtheboxconsultants.com to www.beyondtheboxcic.com. However, my emails have not been changed over. I have three email address which need migrating from @beyondtheboxconsultants.com to @beyondthebox.com.

I have tried to figure out how to do this, via Google Admin and via Square Space, but its beyond my knowledge.

Most importantly, I need to ensure we DO NOT loose the data and details from the current email addresses, and that we set up a re-direct once the new emails are up and running.

Can you help, and how much would this be if you can?

Thanks
Neil