"My father has bladder cancer which has spread throughout his body. I think that cannabis could help him but have been told it's not quite a simple as just going and picking up some from the store. I'm looking for advice on what to get for him."
You need to speak with someone that has a lot of experience treating very sick patients. There are a few well known individuals that specialize in this. You certainly don't want to just go along to your local dispensary and find some cannabis. Here is a link for you. The comany is well known for this type of work: https://www.constancetherapeutics.com/