I don't remember exactly, but I think it had two of them See promotional film. Anyway, it's not a problem, you have to open the casing (Phillips) and inside it's a small Torx? That's all.

Hello, at Digitec, you can order item Nº 5069311 Transcend Jet Drive 520: 240 GB for CHF 199.90 or item 3522112: 480GB for CHF 329.90. Better to buy new than used because after 9 years of use .... it can fail at any time, I just experienced it!

Not that one, but this one (Transcend JetDrive 820 (480GB, M.2, Notebook Package)) should fit. Installation instructions are here: https://www.ifixit.com/Guide/MacBook+Air+13-Inch+Early+2015+SSD+Replacement/38535

Unfortunately it is not. That computer needs a different pinout than the JetDrive 520 model has.