sprite power of two and sprite packer

i am on 2d project with unity curve-animation included

i have imported new graphics from graphic designer and set sprites to advanced with mipmaps enabled and unity warned me that to use mipmaps i need to have textures in POT dimensions (2,4,8,16,32,64,128 ....4096), i completely understand why, however we will have these sprites in spritesheer and i just don't get if each of the sprites (from spritesheet 4096x4096) has to meet the POT condition or just the spritesheet

and if it's the spritesheet so how to turn mipmaps on the spritesheet which is built by spritepacker on build

(i might be missing or misunderstanding something so please help me to understand, thx)