Hi. I assume you have Sub and surrounds?  If so, here is what to do.  (If not, this may be useful to others swapping over)

‘Unbonding’ simply means going into the Playbar settings and tapping to ‘Remove Sub’ and ‘Remove surrounds’.  That is your first step.  (You may be offered to add the Sub to another room, but for the moment just leave it not bonded to any room)

I suggest you then rename the Playbar as ‘Playbar’, unless that is what you already call it. A ‘room’ is really just a label.

Now power off the Playbar and disconnect it from your TV.

Add the Arc, following the prompts and connecting to TV as instructed.  You can give it the same name as you previously called the Playbar, e.g. ‘Living Room’.

Now add the surrounds and Sub to the Arc ‘room’, from the settings for that room.

What to do next depends on what you want to do with the Playbar.  What do yu intend to do?

Yes, unbonding each device from the PLAYBAR is essential. The Sonos software will put them in to their own ‘rooms’, so once they’ve been unbonded, you’ll have extra rooms. Then you will add the Arc (my Arc became ‘Living Room 2’ for a while) and you will set up those extra speakers in the temporary rooms as new surrounds and Sub, this time to the Arc rather than the PLAYBAR. This will move them out of the temporary ‘rooms’ that they were put in when you unbonded them initially, and you will end up with just the one home theater ‘room’ again. Once that happens, you can remove the PLABAR completely, and if needed, rename the Home Theater ‘room’.