This part is hard. Lots of fakes in market. you need to look for local battery specialist.
I bought a whole brick of them from a reputable seller. $7ea at case price/24. Top end Panasonic cells in sealed case.
You also should know not all 18650 are the same. Beyond chemistry some have a regulator build in the end of battery.
Some like laptop batteries do not use a regulator on each battery but use a BMC battery management controller for the whole pack.
You go into Vape Shop and they sell regulated cells. You cannot run them down to zero. They cut out. They also protect against overcharge. Its built into the end of battery like a coin cell but is controller/regulator. You have to cut the first layer open to see it.
The laptop style use a different top because they solder together the cells for series.
My first charger was the VC4. It is good starter model.
There are also RC Car battery packs with some serious punch. They use standard connectors are are easy to work with.
Different chargers on that scene.
I have no dealing with this shop but I noticed they are calling them "Protected Cells".
Samsung 35E Protected 18650—3500mAh, 8A button top. Ideal for flashlights & doorbells. See specs, pricing & fast US shipping at 18650 Battery Store.
www.18650batterystore.com
These cells are midrange.