You will use an internal or external frame pack. External frames are cheaper and will work. Internal frames are more comfortable and quieter for hunting (my preference), especially when hunting in the brush or cliffs for goats and sheep.
You will need at least a 4500 cubic inch external or a 5000-7000 cubic inch internal. If you bring an external pack, get one with a built in sleeping bag compartment. In that case, you will want one that holds at least 5,000-6,000 cubic inches also. Put your backpack (if external type) in a large duffel for the commercial flight as it will be less likely to get damaged by the airlines.
When packing, put the lightest items at the bottom of the pack. Pack the heavy items near your shoulder blade/lower neck level and close to your body. It is better to have a big pack and cinch it up close to your body than to use a small pack and have it barrel out with too much gear.
Barney’s Sport Chalet sells the best external frame packs for hunters. I like their Pinnacle model. Dana Designs, Alaska Gear, Kelty, Gregory, Cabela’s and Camp Trails will all work. The Canadian made Wilderness Wanderer is big and well made, but heavier. I don’t recommend external frame packs for our hunts.
The best internal frame packs I’ve seen are made by Stone Glacier. This is what our guides and myself use. We use the a 7000CI size mostly . Most hunters would be fine with the 6500. Stone Glacier fit and adjust easy for many different users. I would recommend this pack for sheep hunts. “Sky Talus 6900” will be your favourite pack you have had. Its light weight and VERY tough.
There are some other packs that will work in the internal frame market. Mystery Ranch “Marshall” , Kifaru “Duplex Timberline” are the only other two we recommend besides Stone Clacier for Backpack hunts. Period.