How many grafts would I need to get to cover this amount of stubble? (Photo)

Photos cannot determine if you would be a good candidate for surgery.  You need an examination and the doctor needs to understand your goals and expectations.
You need to have good communication with your doctor to understand what your end result will look like.

That's about 1500-2000 grafts but more or lesser that this depends on the quality of your donor hair. The crown area is large, and requires many grafts when emphasized on. Which would leave your donor area over harvested to the point where you don’t have sufficient amount of grafts remaining to fill in the front. So you should see a surgeon and accordingly come to a conclusion.

Beard area may restored with HT. You may have  a hair transplant surgery from scalp skinfollicular units to beard area with FUE to have facial beard hair.If the patient needs a face transplantation as in your case , at least 1000-1500 grafts would better to harvest and transplant to both side of cheek. 

A beard transplant to cover the area you define might take as many as 1000 grafts depending upon the density you want