Not have drawable-mdpi, drawable-hdpi, drawable-xhdpi, drawable-xxhdpi

Question

WorkSpace:Android Studio

I have 35 images. I have realized that I have drawable (but not have "drawable-mdpi, drawable-xhdpi..") folder and also there are "mipmap-mdpi.." folders.

1. I put my images to the simple drawable folder. --> It gives me error: "Canvas trying to draw too large bitmap" I search little bit and I found "Canvas: trying to draw too large bitmap" when Android N Display Size set larger than Small that someone in the link said that I should move images to the "drawable-xhdpi" folder. I tried to move my images to the "mipmap-xhdpi" as you might be know I don't have any type of drawable folders. Only drawable I have.
2. I wanted to use "mipmap" folders for "Images." It works now but maybe it is not best practice
3. After that I have search it little bit and I found Mipmaps vs. drawable folders and someone answered (878 up vote) that mipmap folders is for icons.

What Should I do?

1. Resize the images and put it back to the drawable
2. Do not move your images to the drawable again, it can stay in the mipmap folder no problem. The person in the link said wrong.

Thank you for your attention.

And very very important and last question is should i resize one image into 4 , and put one of them into mdpi, one of them hdpi, one of them xhdpi and one of them xxhdpi? if yes , it means if i have 30 images, i should resize and make it 120 images?