Is this mole cancerous? it had a scab on it at one point or something like that.

It depends: Moles can be cancerous if they are black/brown in color and changing over a period of time. If it has increased in size, then it is best to show it to a doctor who may do a biopsy(to confirm if it is melanoma) or may refer you to a Dermatologist who are better at making a reliable diagnosis and offer appropriate treatment which is usually wide local excision.