Help SN testing kit

[YandereMikuMistress]

Im wondering weather or not to buy this
I'm not entirely sure what kind of testing kit I'd need to use for SN but I'm assuming somthing like this, though that's why I'm hoping for some help with any information on this sorta thing, so if your willing please pm me or message here either or really
Or mabye something like this?
Or possibly somthing like this

only difference is I'm not sure how to purchase this one yet, I got a website but haven't looked into it

 

[sewycidial]

I would buy it if I had a source on SN

 

[Mayonaise]

Generally speaking, test strips are less accurate than reagents test (the ones with the tiny little bottles). The first picture you posted refers to a nitrAte (NO3) test and won't be any good. The second one is a strip test for nitrites (NO2) and may be good, the last one is for NO2 too but is a reagents test and should be more accurate.
I never used such a testing kit yet but I'd suggest using a JBL ProAquaTest NO2
This post shows an example on measuring the desired quantity of SN for such a test. If you use the JBL testing kit, you must have 1mg/L in the testing bottle.
This thread features images of the procedure but is referring to a different test kit and thus uses a different SN concentration