Using different 18650 to repair laptop battery
Don't mix different batteries!
(unless you know very, very well what you are doing)
The battery management system is probably going to keep them from exploding, but they will not work as intended and will probably fail quickly.
If you have a balancing charger/analyser and a lot of patience, you may be able to measure the capacity of all the cells that you have and match six of the available that are within 5..10% capacity difference.
p.s. don't be tempted to replace the cells with much more powerful ones. The battery management may not like them much. More powerful ones are also more picky about charging conditions.
10% or 20% over is probably OK.