Tried switching to Ubuntu and cannot get back to Windows

Okay, this is a bit of a longshot but I am looking to try and fix this again

Over a year ago now, I was curious to try something out that I could only do on either a Mac or Ubuntu, and so I went ahead with downloading it onto a flashdrive and running it on my Acer Aspire laptop. I ran into a problem though that for some reason my laptop just automatically bypassed allowing you to open the BIOS to switch it in the first place, so after a bit of googling I learned I needed to do some kind of special restart that I found in the Control Panel.

After I did that, I still couldn’t find the option to run Ubuntu. I did some googling again and found that I needed to switch up the start up style (either from Legacy to UEFI or the other way around, honestly it was so long ago I can’t remember).

After doing that, Ubuntu just ran automatically without even needing to open BIOS. The problem now though is that I guess because of the way this laptop is designed, I can’t get back to BIOS again without that special startup. What do I do? I am only on the Try Ubuntu because I am afraid of wiping my Windows or something if I install the full version of it.

Any advice? I’ve been using my iPad exclusively for over a year now, but I would like to get back to this laptop if I could.