Moving Disk Shelf to New Controller

Hi Everyone,

I'am asking for any suggestion or best practice for my scenario below.

Our customer have an Existing FAS8040 dan 6 DS2246 & 2 DS4246, and we are planning to move those 6 DS2246 + 2 DS4246 to New Controller FAS8300 with 4 DS224C. What is the best step to move all the exisiting Disk Shelf to New Controller without removing all the datas? (except vMotion or anything else because the New Controller capacity are not enough as existing capacity)

also for the information:

Existing FAS8040 Capacity 285TB Running ONTAP 8.3.2

New FAS8300 Capacity 52TB Running ONTAP 9.9.1

Any suggestions/best practice are welcome.

Thanks!!