adapter for MacBook SSD

I don't think that's the right model number. You're reading this off the back? Should be MZ-numbers and letters here. 256ssubx there doesn't pull up anything useful. Alternatively what's the model number of the macbook air?
 


 
Well...there are adapters like:
https://www.amazon.ca/Sintech-17Pin-Adapter-MACBOOK-Retina/dp/B00SLI1YNK?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duckduckgo-d-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B00SLI1YNK
that will let you use it as a sata drive. While I think by itself that drive might fit on an m.2 slot on a mobo, not sure if it's compatible with whatever you have on your board connection wise. Unless you can check with a manufacturer of your mobo, an adapter and then plugging in via sata might be safer.
 
The Macbooks (Air and Pro) use a proprietary connector for their SSDs. It looks like M.2 but it's not. In addition, Apple has tweaked the port at least once to try to thwart OWC's aftermarket SSDs - Apple began encrypting the datastream between the mainboard and drive. That's why the above linked adapters only works for 2012 Macbooks or earlier.

As yours is a 2015 model, I don't think there's any adapter which will let you use your Macbook SSD plugged into a regular SATA or PCIe port. AFAIK, OWC is the only company that has managed to crack Apple's encryption. You can try contacting them to see if they have something which will work.

https://eshop.macsales.com/shop/ssd/owc