Computer wizards, I need help with a Windows 10 install please!

Good day again to all these people who know way more about computers than me and are generous enough to educate the ignorant,

I have a problem and don't know where to find the answers I seek:

I was given an old Acer that I need to put back into commission because it is one of the few Windows devices we have, and I need at least a Windows 8 device to support a vital application we need going forward in our operations.

It had Windows 7, so I chose to upgrade for Windows 10 because this tutorial was very easy to follow, and why not use the most updated OS if I can.

After MANY hours (which seemed excessive) of waiting for my computer to think through all the "checking for update" phases and whatnot, I finally got to the 1st reboot (of what I understand should be a total of 4 reboots in a Windows 10 upgrade).

And what joy and relief to finally arrive here!

UNTIL...

This computer has both Windows 7 and Ubuntu loaded, and upon start up the user sees first the Acer logo, then is prompted to choose which OS to use.

I chose Windows 7, and was met with a solid black screen and a shrill, disheartening beep code that stops only when I push the power button.

So I tried all the options with the same horrible result (except when I chose memory test, which takes me to a blue screen with a bunch of info most of which I don't understand).

I assume the error comes because I want to reboot/access with Windows 10, but start up gives me only Windows 7 option so this command confuses the computer...but IDK.

WHAT IS GOING ON, AND WHAT DO I DO??

This troubleshoot article is more advanced than my current skillset, but it suggests that I "ensure the source OS is stable. Also ensure the Windows setup source and the destination drive are accessible" IF it is indeed a downlevel error.

SO my questions are:

1. IS this a downlevel error? If not, what is going on?
2. If it IS a downlevel error, how do I "ensure the source OS is stable"?
3. How do I "ensure the Windows setup source and the destination drive are accessible"?
4. How do I access ANYTHING other than this start up menu of OS options and the awful beep with black screen?

Ultimately, how do I fix it??

Any advice would be appreciated.

Thanks in advance.

✨💫💛💫✨ Sara!