I want to change from High Sierra 10.13.6 to Mojave 10.14.6 to so I can buy Final Cut Pro X Help

I have a Macbook Pro late 2013 High Sierra Version 10.13.6 and in order to buy and download Final Cut Pro X I need to Install Mojave 10.14.6 which I have downloaded but now that won't load and is telling me I need version 10.14 which I can t find anywhere on Apples software downloads. I am worried if and when I find that version 10.14 it will tell me I need another download. Can someone please tell me how I can do this. I am stuck at home because of Corona virus and my internet took around 6-7hours to download Mojave 10.14.6 and I would like some advice that avoids to many more attempts to sort this out. Thanks