I'd consider those batteries a scam.
The dimensions given for that battery (110 x 70 x 20mm) are just big enough for six, 18650 cells. It's totally impossible to get 30AH in that.
It's likely an accidentally-on-purpose extra zero in the print, which I've seen many times on ebay aliexpress etc. batteries and cells. Or, some sellers add the capacity of the series cells, another scam.
Plus from the way the shrink sleeve shows the ends of the cells etc., there does not appear to be any protection / balance board included, which makes it an accident waiting to happen!
Build your own, it's safer and will have genuine capacity.
To duplicate that you need several three-cell chains in parallel, plus a decent three cell balance and protection board.
I posted a similar setup for another user, showing both a six cell (3S2P) pack with protection board, and the charge / bypass circuit to make it work as a "UPS" type system.
You could also get some big RC flight batteries - they are reasonably cheap, eg. three cell 6AH
Smarter Shopping, Better Living! Aliexpress.com
Add a balance / protection board as above. You could parallel them for higher capacity, either directly once you have charged them to exactly the same voltage, or add a balance board to each to make two-terminal packs like mine, then parallel them.