what single speed adapter can i use ?

hello
I am new to the site and very new to electric bikes I am building a Schwinn occ stingray chopper and have many questions and need major help right now I am trying to figure out what single speed cassette adapter I can use on the bafang 500watt 170mm rear hub motor I purchased I am hoping I can use the 15 dollar fixie shimano single speed conversion kit I purchased it has not arrived yet and the motor is on its way to a wheel builder to lace it in a 100mm stingray fat tire rim I sent him the fixie thing hopefull it will work and if not it was only 15 dollars not a big loss if it wont work does anyone know if it will work or not please let me know I will periodically post my progress on the build and also be asking many many many lol more questions as I really have no idea what I am doing but due to lack of resources I have no choice but to do this my self I will be using the motor I describe above on the bike I described and will be using a battery pack any where between 48 volts to 72 volts depending on prices I also would like to use a regular motorcycle headlight cause I like the look of them rather than a bicycle light but I do not know if I will have to use a separate 6-12 volt battery for it or if I can somehow wire it to the motor controller or directly to the battery using a voltage step down converter or something of that nature but that's is a long way off anyway thanks for any help and suggestions are very welcomed and needed thank you sincerely Jaymus

Is your motor threaded for a freewheel or splined for a cassette? People use the terms interchangeably, but cassettes and freewheels are not interchangeable.

In either case, it's an easy job. You can get 15t to 22t single freewheels, or you can use a cassette sprocket from 13t on up. The cassette sprocket offers you more control over chainline.