Step 1 : Enable remote access for MySQL server using the documentation at MySQL Remote Access . You do not need to open port 3306 unless you require to provide access to the outside world.

Step 2 : Refer to steps 4 and 5 of the above mentioned documentation, and add the following value in the 'Additional Access Hosts' field.

172.16.26.%

Step 3 : In your NodeJS codebase or in the concerned .env file, use the value 172.16.26.1 as the DB Host

Using the above steps, your NodeJS App should be able to access MySQL server on the N99panel VPS.