Change User names on new mac?

I want to 'migrate" from a Catalina MB Pro to a new iMac. The only thing I want to change is the user names, ( e.g. Robert change to Robert22) but keeping the contents of the old user to the new user. So the Robert22 user folder would be identical to Robert. There are 2 different users that I want to change, the second account being a standard account and Robert22 the main admin account.

I am not sure that migration assistant would do this.

What's the easiest way to do this?

Thanks