I am looking to inactivate g,kg, and oz from the weight field on an item record ( field name is weightunit ) but I am unable to find where this is managed. Can anyone confirm that this is possible and if so point me to where I can find them?

Not 100% sure what you're trying to do there but you probably want to global search "units of measure"

yeah, that page is empty. Basically all our UOM are "lb" we want to remove the others to prevent any data entry errors

If you have no unit of measure for kg etc I don't know how you would be able to select it unless that field is not the native NS one, in which case you need to find the list / record being used.