Static IP address for a NAS is generally a good thing.
Just to make things cleaner, you might want to assign the IP address From the router and not from the NAS.
This would avoid unintended problems if you get a new router that does IP address assignments in a different subnet than you NAS is requested. This might result in loss of access to the unit.
(and while you are at it. . .you might want to see if your ROUTER can block all internet access to a MyCloud Gen 1 device that is running OS/3 - - - > From a security perspective, this is not the most secure device around)