The tire size for your bike is 26" x 2.8" so most any tube labeled from 26 x 2.5 to 3.0" should work just fine. If you can't find those, 27.5 x 2.8" will also work. Your bike uses Schraeder valves, which are quite common on cars, but less common on high-end bicycles. If you need to use a Presta Valve tube, it will work just fine, though it may make a little noise since it's smaller than the Schraeder valve.
Your local bike shop will likely be the cheapest source for tubes, though they may have to order them. I normally like to send an Amazon link here, but the Amazon sources lately have not been great quality. If you need to order online, Schwalbe is a great source. I can't give you a direct link but if you set up the tube finder like shown, you'll get the right tubes:
In the example above, the only difference between the tubes is their weight. The 'Downhill' tube is heavier, and offers a bit of puncture protection. Personally, I'd get the lighter tube and use a sealant.
Inner tube sealants have come a long way from the old green slime, which was more of an 'it'll get you home' solution. Moder sealants can repair the puncture permanently. I recommend the following, in this order:
Muc-Off Inner Tube Sealant