If they're M.2 NVMe not M.2 SATA. I don't think such an adapter exists. It likely isn't possible. At least without a lot of expensive hardware to convert.
Startech just released an M.2 NVMe to USB 3.1 Gen 2 enlosure. Everything else external, I believe, requires Thunderbolt. If you want full speed anything other than Thunderbolt 3 enclosures are pointless. Well Thunderbolt 2 may be good enough but hardly any PCs have those and I believe all the Thunderbolt NVMe enclosures are Thunderbolt 3 and I don't think anyone makes an adapter to go from a Thunderbolt 3 peripheral to Thunderbolt 1/2 computer.
https://www.startech.com/HDD/Enclosures/usb-c-m2-drive-enclosure~SM21BMU31C3
They do may an M.2 to SATA adapter. NVMe is not supported. Just M.2 SATA models.
https://www.startech.com/HDD/Adapters/M-2-SSD-2-5-in-SATA-Adapter~SAT32M225