Better to be seen in person
It is very hard to give you an actual amount on what you would actually need just based on your pictures. I would recommend that you come in for a free consultation seeing as you are in the Ontario area. A rough guess would be around 1000 (give or take) if you wanted to achieve some density again in that area. In my opinion it never hurts to treat this now instead of waiting for future procedures because you can do some preventative maintenance now and then if an amazing more effective procedure comes along in the future you can use that for any future thinning or balding you may have.
How many micrografts do I need to help my hair loss?
Hair transplants have come a long way since Biden had his done! Now, I use a machine that harvests the grafts and I normally do not take a strip anymore. Then, the micro grafts are placed where the patient wants them. Also, the amount that I can insert of the mini grafts can be 2000 plus in one session!
800 - 1200
I would be conservative given your age. The donor hair is a valuable resource. 800 - 1200 grafts is more than enough to fill in your air. I'd avoid strip methods and perform FUE to avoid giving you a big scar running across the back of your head. You may find the attached video helpful, but if you want to observe an actual hair transplant you can arrange with the office with approval from our patient, of course (we are having one this Saturday).
Hair Line restoration
You appear to be a good candidate from your pictures and a smaller case of 1000-1400 Follicular Unit grafts may be adequate, but you should be seen in person if possible. See link below to a younger patient with curly hair on whom I performed hair transplantation.
How many grafts
I would assume that your hair is of a medium weight or better as fine hair generally takes more grafting. I would expect that something in the range of 1000 grafts might do it. There is no substitute for a one on one with a doctor. This coming Saturday, we have an open house in our office between 11-2pm and there you will have an opportunity to receive a free consultation with a doctor, see a surgery and meet many patients who have had hair transplants. I always tell people who are shopping for a hair transplants, meet patients for what you see is what you are going to get.
Normal density of hair for a caucasian male is about 200 hairs per square centimeter so you can work backwards
Normal density of hair for a caucasian male is about 200 hairs per square centimeter so you can work backwards to see how many hairs you would need to get full thickness.
Frontal Hair Loss
It seems like you are having class III hair loss which is limited to the frontal and corners. You need a microscopic evaluation to see if you have evidence of hair loss on the more posterior areas, but based on what I can see your need should be limited and 1500 - 2000 grafts can give you a good density in the frontal areas which is about 1-2 inches. You can check similar patines in our website. They could be found under photo galleries and to make it easier we organize them into different classes.