Autobiography, memoir or novel?

Illustration: Susanna Kajermo Törner

A while back I took a notion that I would tell the story about the kind of childhood that my brothers and I had in the 50s in Finland.  My brothers are no more. I am the only one left so I had to catch this fast fading childhood by the tail and pull it back if I wanted to make a record of it.
But would it be an autobiography or a memoir?
Hardly an autobiography because such mighty tomes are written by men of national or international importance. A memoir then?  Tove Jansson's Moominpappa says that if you are a 'father of a family and an owner of a house' you can poise your memoir-pen and start. He also says 'Everyone, of whatever walk of life, who has achieved anything good in this world, or think he has, should, if he be truth-loving and nice, write about his life,  albeit not starting before the age of forty'. It sounds as if it could be a convoluted and lengthy business.
It will have to be a novel I thought. It would give me the freedom to boil down many samey events to one intense event. And by tweaking the story a little  I could give it a better structure. But my story would still be true in its essence.
And all the paper I would save!