I use 18650’s in all my vaping mods and all a higher capacity than those in your pack so very common thing to find.
I noticed they are INR cells and will have just dropped below required minimum voltage for your standard charger so with the correct charger they can be revived no problem, plenty of threads on vaping forums about what type of charger to purchase and how to go about it.
Unless you know how to solder and build a battery pack safely then I would leave that idea well alone, I’ve made a couple to replace some SLA batteries for a scooter using LifeP04 cells and it’s not simple to say the least.