A couple of good ways to check for the SIM card version you need:
Enter your IMEI/IMEID on this Sprint Bring-Your-Own-Phone page, and click through a couple of steps to see the specific SIM card model you will need:
Or, the s4GRU Sprint SIM compatibility crossreference table is considered the 'gold standard', and is compiled directly from info sourced from Sprint:
The s4GRU chart can be a little confusing to read, at least until you get used to it.
One of the odd things is understanding the difference between the 'Primary' and 'Secondary' SIM listings. 'Primary' SIM is the SIM that would be used in a Sprint-branded version of a phone. 'Secondary' SIM is the SIM card that would be used in the same model # phone, but originating as either an other-carrier version (perhaps a T-Mobile branded phone that had been unlocked from T-Mobile), or a factory-unlocked version of the phone. Note that the primary and secondary SIM cards are not always the same.
(The tertiary and quaternary columns are newer, and I haven't figured out the implications there, yet. Maybe it includes info about an earlier model SIM card that has been superseded by a later model? )
The s4GRU chart provides the SIM card # itself, the Sprint part # (which is different), and the UPC code. (Resellers may list any one of those 3 numbers), as well as the Universal SIM Card Kit that contains the SIM you need (if it's available in the Universal kits.)
As an aside-- you'll see SIM cards listed with prefixes SIMOLW and SIMGLW prefixes. (O vs G.) This letter only indicates the original factory/manufacturer of the SIM card, and whether it was intended to be utilized as a delivered-with-the-phone SIM, or an after-the-sale SIM card. The O and G models are interchangeable.
(EDIT: TO ADD A CORRECTION)
The Sprint test page linked above probably wasn't the best recommendation, since it will only work with a phone eligible for Sprint Postpaid service. (Factory Unlocked, carrier unlocked, or Sprint Postpaid branded.)
Instead, Tello's BYOD page now also identifies the needed SIM card type, and should work with all of those types, plus devices originally branded by Boost, Virgin, etc.
Please remember, though, that if you have one of those prepaid phones with the original SIM, you should just use the original SIM. If you bought the phone used from a vendor that removed the SIM card before sale, the Tello site is an easy way to ID the needed SIM type.