Not able to start the Ubuntu

I upgraded my Ubuntu from 18.04 to 19.04, but now when I’m starting the system, it isn’t starting. Just a purple screeen is showing up. When I tried the recovery mode, it’s showing a black screen with the following message

[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0, 0) ] - - - 

Also it’s not giving options to type anything.

enter image description here