MacBook Pro Internal Hard Drive dead?
Not withstanding Nimesh's comment and presuming that method does not work...

Installing Mojave was undoubtedly not the cause of this issue, more like just coincidental. That said it is likely that something has happened to the HD (or SSD) in your MacBook pro.

It could be a loose connection, it could be a damaged/dead drive. heck it could be a number of things. But the one thing they have in common is that it is likely that the MacBook will need to be opened and serviced by a tech competent in doing said work.

If it is within warranty take it to your nearest Apple store. If there is not an Apple store nearby, call Apple tech support.

If it is out of warranty you can still take it to Apple but they will charge you for the fix. Possibly more than an independent Apple dealer might. But that would be your choice and based on your local experience with Apple stores, dealers and the repair jobs they are experienced with.