MacOS X Version 10.8.5

I've read were this has been asked multiple times with varying answers. I've purchased an older Macbook Pro to use to run my music mixer and software. My buddies 2012 Macbook Pro runs circles around my $2500 Windows PC. The problem that I'm facing is that I am unable to update the software.

This could easily be user error as I'm new to using a Mac, but I'm pretty technically savvy in the Windows world. Anyway, there's the issue:

I've tried to install El Capitan, Sierra, and Catalina. Catalina version requires 10.11 (I believe) so I've downloaded the other aforementioned OS versions. I go through the installation via the InstallOS.pkg file that I downloaded. I go through all the steps and at the end, it says that I successfully installed the new OS. But, nothing happens even when I reboot. I'm assuming that it's similar to windows where you need to run an external device to upgrade. With that in mind, I've been trying to use an external flash drive. I've formatted the drive, but still have issues.

At first it was saying that createinstallmedia didn't exist for El Capitan and Sierra. I believe that I figured that out by adding a --nointeraction at the end of the sudo... string. Now it's saying the /Volumes/Untitled is not a valid volume mount point. I'm not sure what to do now. Please advise.

Specs:

MacBook Pro 13", Mid-2012

Processor: 2.9 GH Intel Core i7

Memory 8 GB 1600 MHz DDR3

Graphics: Intel HD Graphis 4000 512 MB

Software: OSX 10.8.5 (12F2560)

HD: 750 GB SATA HD