NDM wallets can be imported into MetaMask as a Keystore file. To do so, follow the instructions at https://metamask.zendesk.com/hc/en-us/articles/360015489331-Importing-an-Account, choose JSON File as the type, and then when prompted to select your Keystore file:
locate your NDM installation folder
navigate to the keystore
folder
select the file that has your Ethereum address in the name
NDM wallets can be imported into MyEtherWallet as a Keystore file. To do so, follow the instructions at https://kb.myetherwallet.com/en/getting-started/how-to-access-your-wallet/#Keystore-JSON-Password and when prompted to select your Keystore file:
locate your NDM installation folder
navigate to the keystore
folder
select the file that has your Ethereum address in the name
Consumer and provider wallets in NDM can be imported into MyCrypto as a Keystore file. To do so, follow the instructions at https://support.mycrypto.com/how-to/accessing-wallet/how-to-access-your-wallet-with-keystore-file and when prompted to select your Keystore file:
locate your NDM installation folder
navigate to the keystore
folder
select the file that has your Ethereum address in the name