MB Pro 2015 have NVME PCIe SSD which are super fast. I was thinking to replace mine with a bigger capacity one. And then use the old one in a Windows laptop, if that's possible. Since my Windows laptop have SATA SSD I need an adapter, so NVME PCIe SSD to SATA adapter exist?
I don’t recommend doing this.
First off, finding an Apple proprietary NVMe adapter to put into a PC is next to impossible. You’re more likely to find an NVME adapter that goes from the industry standard M2 to Apple’s proprietary format. My guess is that the market is too small - there simply isn’t enough Apple NVME SSDs in the wild where people want to install them into PCs.
Secondly, that Apple NVME SSD is super fast and connecting it to a SATA interface will just slow it down; you’ll never get the speed out of it once you connect it to a SATA interface.
Instead, sell the Apple SSD (they do go for quite a bit of pocket change) and get a standard SSD instead. Save yourself the headache of trying to convert.
You'd need SATA at one end and Apple's own "12+16-pin" PCIe connection, which is different from the M2 industry standard connectors used on SSD blades in other PCs.
You can do your own searching, but I suspect such things are hard to find. You would have more luck with adaptors that connect an Apple SSD blade to a USB port as an external drive, but these can be expensive.