How many grafts will be required to cover this whole scar? Planning for FUE. (photos)

Without seeing you in person and measuring out the area it's hard to say, I'd guess a few hundred at the least.  You may also want to consider scalp micropigmentation as an option.

Thank you for your question,  if we do a Hair transplant in this area the entire scar may not be hidden because we can not achieve the density which is there naturally . so when your hair are really sort there is a definite possibility that the scar will be visible, however the visibility will be much lesser as compared to the current condition. and if you keep you hair longer the scar will not be visible. you may think of combining micro pigmentation along with hair transplant to achieve better results or you can go in for a scar revision, it is to basically reduce the width of the scar followed by a hair transplant. if you go for a hair transplant you need to consider the trycophytic closure to allow hair grow from the scar itself.