Item Unit of Measure


I have an item (Item A) which was setup incorrectly in terms of uom.

ITEMA 1 GR - this is where the problem starts as it was supposed to be 0,001

Sales and purchases have already been posted and obviously the cost is now quite messed up.

Is there a way to fix this, like a reconcile or adjust cost function, or some type of function where I can fix the UOM and run it, which will in turn fix the costs?
If not, could someone kindly advise me on possible solutions?

Thanks all.