So you bought 3 new shelves (or used) at this point for your 3070. Are they FC shelves? You can only add 6 shelves per fc loop, so you have to start another loop since you have 3.
Are you running MPHA, you should really run config advisor and hopefully your netapp sales team can assist you. Althought a 3070 is very old at this point.
I assuming you are runnin 7.x at this point