I'll keep it short - the migration to pro is wildly difficult.
In your experience, what's the best way to migrate macs from Now to Pro? Just under half of the devices are in ABM
I've done this with some smaller companies we've acquired over the last couple years. For devices that are in ABM, we added those devices to JamfPro and then had users reset the devices so that they'd be good to go. For those not in ABM, we were doing wipes and then manually enroll them. It all depends how many devices you are looking at doing this all to. Now with Apple Configurator for iPhone, if its a small amount of computers and they are T2 or higher running Monterey, you can add them into your ABM with the Configurator App.
you could setup for self enrollment.. but if your end users are anything like mine that may be asking a bit much. That said I would probably use configurator to put devices in ABM as already pointed out. Hope you dont have any other major projects pending.