Linux kernel version with (uname -r) does not show distribution version, where can I get the kernel source for this kernel?

I’m trying to compile a specific kernel module for my linux machine running on a hosted dedicated VPS. The VPS instance is running Ubuntu 20.04 64bit.
In order to get the source code for the kernel I need to find out the exact kernel version. When I run uname -r I get this value: 5.4.0

Since there is no hyphen in the version number I’m not sure where to get the source code and kernel headers for my kernel.

Sorry if the answer is obvious, I’m not very experienced with Linux.