From your post you sound like youngster/minor or someone with little if any experience.
5 posts and all of the "Sanwu help" posts for help with simple tasks of ordering , receiving, and putting batteries of a laser which is the same task as a ordering. receiving, a torch/flashlight and putting batteries in it.
If you are a minor, be sure to tell your parents what you are doing as they are responsible for anything that happens to you or to others as a result of what you do.
If you have sleeves to adapt the 26650 battery tube to the smaller diameter 18650 -- common sense should tell you that if you have a way to make them fit properly they will work just fine, just a shorter time between charges due to lower mA capacity.
Note: If you don't have them already,>>> more important than batteries<<< is that you have proper good quality eye protection/laser glasses/goggles before you fire up a 1.2W green Striker which is a dangerous laser that can permanently damage your eyes in less than the human blink reflex time of 0.25 seconds.
You can get an Eagle Pair, least expensive good quality laser glasses/goggles, here for $44 to $49:
https://www.survivallaser.com/Safety_Goggles/cat556089_826120.aspx
Or you can get am Eagle Pair in the UK at Otic Force:
https://odicforce.com/epages/05c54f...fb6-7778-4d36-adc0-0098b2af7c4e/Categories/36
You really need to study up on laser safety/safe use procedure as well since you don't seem know what you are doing or why at this point --see best web site about same and related here:
https://www.laserpointersafety.com/
See Laser Hazard Chart here:
https://www.lasersafetyfacts.com/resources/FAA---visible-laser-hazard-calcs-for-LSF-v02.png
See what happened to an LPF member in less than 1 Second from being hit in the eye with a 1W laser:
https://laserpointerforums.com/threads/hit-in-eye-with-1000mw-445nm-blue-laser.69469/
also yes I don't have much experience with them I have had a few cheep laser 303s in the past so I've jumped from a claimed <5mw laser to a 1.2w laser I knew the 18650 batteries would fit and I have just tried it, it's not getting enough power I think as its really dim so I'll just have to be patient for my 26650 batteries to arrive 