mine are too low and want them higher
I would build a base - maybe out of 2 x 4's and set the cabinets on that to make them higher.
Upper or base cabinets?
Is there room above cabinets to move them up? Are you asking about upper cabinets or raising the lower cabinets. It would be easier to move cabinets up rather than cut them down if can.
You can cut them with a reciprocating or circular saw, depending on if you need a more precise cut or just a chop
You will need to remove upper cabinets and basically take then apart to rebuild to trim off fronts, wall sides and back. Save the top.
Depending how much you need to take off, may have to totally remake front rails and doors. Using a table saw would work best.
Would be easier to just get new uppers or just put up open shelves like Joanna Gaines does in her remodels.